Intranuclear protein transduction through a nucleoside salvage pathway

ABSTRACT

Provided herein are conjugate molecules containing a substrate for a nucleoside transport pathway linked to an active agent, wherein the conjugate can be transported into a cell or into the nucleus of a cell via a cellular nucleoside transport pathway. Further provided are methods of delivering a conjugate molecule to a target cell expressing a nucleoside transport pathway, wherein the conjugate contains a substrate for the nucleoside transport pathway linked to an active agent. Also provided are methods for screening for conjugates that are transported by nucleoside transport pathways. Further provided are methods of treating a patient having a disease or disorder affecting tissues expressing nucleoside transport pathways, in which a conjugate containing an agent effective in treating the disorder is administered to the patient. Also provided are methods of treating a patient having an autoimmune disorder involving administering to the patient a compound that inhibits a nucleoside transport pathway.

RELATED APPLICATIONS

This application is a utility application and claims priority under 35U.S.C. §119(e) of U.S. Provisional application Ser. No. 60/931,855 filedMay 24, 2007.

FIELD OF THE INVENTION

The present invention relates generally to conjugate molecules and morespecifically, to conjugate molecules and their use in the delivery ofactive agents into cells using endogenous cellular transport pathways.

BACKGROUND OF THE INVENTION

Transporter proteins are involved in the cellular uptake of variousmolecules into and/or through cells. Carrier-mediated transport systemsuse proteins that are anchored to the cell membrane, typically by aplurality of membrane-spanning domains and function by transportingtheir substrates via active or passive mechanisms. Carrier-mediatedtransport systems are involved in the active or non-active, facilitatedtransport of many important nutrients such as vitamins, sugars, andamino acids. Carrier-mediated transporters are also present in organssuch as the liver and kidney, in which the proteins are involved in theexcretion or re-absorption of circulating compounds. Polar orhydrophilic compounds typically diffuse poorly across the lipid bilayersthat constitute cellular membranes. For many small molecules (e.g.,amino acids, di- and tripeptides, monosaccharides, nucleosides andwater-soluble vitamins) there exist specific carrier-mediatedtransporters for active transport of the solute molecules acrossbiological membranes.

The uptake or release physiological nucleosides and many of theirsynthetic analogs by mammalian cells occurs primarily by means ofspecific carrier-mediated transporters known as nucleoside transporters.Nucleoside transporters have been classified into two categories: (i)equilibrative (facilitated diffusion) and (ii) concentrative (secondaryactive) sodium-dependent. Two equilibrative transport systems withsimilar broad substrate specificities have been identified anddesignated as the es (equilibrative sensitive) and ei (equilibrativeinsensitive) transporters, on the basis of their sensitivity orinsensitivity to inhibition by nitrobenzylthioinosine (NBMPR, 1),respectively. As many as six sodium ion-coupled (concentrative)nucleoside transport systems designated cif/NI, cit/N2, cib/N3, cit/N4,cs/N5 and csg/N6 have also been functionally identified in mammaliantissues.

The anti-DNA antibody fragment 3E10 Fv has been demonstrated to be anovel molecular delivery vehicle due to its penetration into livingcells with specific nuclear localization, absence of toxicity, andsuccessful delivery of therapeutic cargo proteins in vitro and in vivo.Elucidation of the pathway that allows 3E10 Fv to cross cell membranesis critical to the development of new molecular therapies, which rely onthe regulation of gene expression by intranuclear transduction ofmacromolecules.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that a DNA-bindingantibody that can penetrate cells and localize into the nucleus istransported by a nucleoside transport pathway.

According to one embodiment of the invention, there are providedconjugates including a substrate that is capable of being transported bya nucleoside transport pathway, and an active agent linked to thesubstrate, wherein the conjugate is transported by the nucleosidetransport pathway. In particular embodiments in which the substrate isan antibody, the antibody is not the monoclonal antibody 3E10 or afragment thereof. In certain embodiments, the nucleoside transportpathway includes an equilibrative nucleoside transporter or aconcentrative nucleoside transporter. In embodiments in which thenucleoside transport pathway involves an equilibrative nucleosidetransporter, such a transporter may be insensitive to inhibition by lowconcentrations of nitrobenzylmercaptopurine riboside (NBMBR).

According to another embodiment of the invention, there are providedmethods for delivering a conjugate to a target cell expressing anucleoside transport pathway. Such methods involve contacting the targetcell expressing the nucleoside transport pathway with a conjugateincluding a substrate that is capable of being transported by anucleoside transport pathway, and an active agent linked to thesubstrate, wherein the conjugate is transported by the nucleosidetransport pathway. In particular embodiments in which the substrate isan antibody, the antibody is not the monoclonal antibody 3E10 or afragment thereof. In certain embodiments, the nucleoside transportpathway includes an equilibrative nucleoside transporter or aconcentrative nucleoside transporter. In embodiments in which thenucleoside transport pathway involves an equilibrative nucleosidetransporter, such a transporter may be insensitive to inhibition by lowconcentrations of nitrobenzylmercaptopurine riboside (NBMBR).

According to a further embodiment of the invention, there are providedmethods of screening a conjugate for transport by a nucleoside transportpathway. Such methods include, contacting a cell expressing thenucleoside transport pathway, with a conjugate under suitable conditionsfor transport to occur; and determining whether the conjugate istransported into the cell by the nucleoside transport pathway. Incertain embodiments, the determining step includes comparing the amountof conjugate transported into a cell expressing the nucleoside transportsystem to the amount of conjugate transported into a control cell notexpressing the nucleoside transport system. In these embodiments, anincrease in transport of conjugate of the cell expressing the nucleosidetransport pathway as compared to the control cell indicates transport isby that nucleoside transport pathway.

According to yet another embodiment of the invention, there are providedmethods for treating a disease or disorder in a cell or tissueexpressing a nucleoside transport pathway. The method includesadministering to a patient having the disease or disorder a conjugateincluding a substrate that is capable of being transported by thenucleoside transport pathway expressed in the affected cell or tissueand an active agent for treating disease or disorder, wherein theconjugate is also transported by the nucleoside transport pathway. Inthis way, the conjugate is transported into the affected cells ortissue, thereby delivering the active agent. In certain embodiments thedisease or disorder involves skeletal muscle and the conjugate istransported into the skeletal muscle cells, thereby delivering theactive agent.

According to yet another embodiment, there are provided methods fortreating a genetic disorder wherein the method includes, administeringto a patient having a genetic disorder a conjugate including: asubstrate that is capable of being transported by an equilibrativenucleoside transporter, and an active agent for treating the geneticdisorder, wherein the active agent is linked to the substrate, andfurther wherein the conjugate is transported by the equilibrativenucleoside transporter, whereby the conjugate is transported into cells,thereby delivering the active agent. In certain embodiments, the activeagent is a gene or protein that is deficient in patients having thegenetic disease.

In other aspects, this disclosure provides a method of treating acancer, wherein the method includes, administering to a patient havingcancer a conjugate including: a substrate that is capable of beingtransported by an equilibrative nucleoside transporter, and an activeagent for treating cancer, wherein the active agent is linked to thesubstrate, and further wherein the conjugate is transported by theequilibrative nucleoside transporter, whereby the conjugate istransported into cancerous cells, thereby delivering the active agent.In certain embodiments, the active agent is a tumor suppressor gene ortumor suppressor protein.

According to still another embodiment of the invention, there areprovided methods of treating an autoimmune disorder includingadministering to a patient having the autoimmune disorder a compoundthat inhibits transport by a nucleoside transport pathway.

The present disclosure also provides a pharmaceutical compositionincluding a conjugate described herein and an agent that promotes ENT2expression in a tissue. In some aspects, the agent that promotes ENT2expression in a tissue is an agent that treats or inhibits hypoxia or anagent that inhibits HIF-1. The tissue may be a hypoxic tissue, such as ahypoxic tumor, a tissue with insufficient vasculature, an ulcer, adiabetic ulcer, a poorly-healing wound, an ischemic area, an ischemicarea resulting from stroke, or an ischemic area resulting fromcardiovascular disease. In certain embodiments, the agent that inhibitsHIF-1α is a siRNA, an RNAi construct, a hairpin RNA, or a miRNA thatreduces HIF-1α expression. In some embodiments, the HIF-1α inhibitor isa chemotherapeutic drug, topotecan, NSC 644221, PX-478, YC-1,17-AAG, orbevacizumab. In certain embodiments, the agent that treats or inhibitshypoxia is an agent that normalizes tumor vasculature, or an agent thatalters the redox state of a tissue. The agent that treats or inhibitshypoxia may be excess oxygen, TSC, or almitrine.

Furthermore, herein is provided a method of treating an ENT-2 deficienttissue, wherein the method includes: a) administering an agent thatpromotes ENT2 expression and/or activity, and b) administering one ofthe conjugates disclosed herein.

DESCRIPTION OF THE FIGURES

FIGS. 1A-B show the nucleotide sequence (SEQ ID NO:1; GenBank AccessionNo. U81375) and amino acid sequence (SEQ ID NO:2; GenBank Accession No.AAC51103.1) of human ENT1, respectively.

FIGS. 2A-B show the nucleotide sequence (SEQ ID NO:3; GenBank AccessionNo. AF029358) and amino acid sequence (SEQ ID NO:4; GenBank AccessionNo. AAC39526.1) of human ENT2, respectively.

FIG. 3 shows the nucleotide sequence (SEQ ID NO:5; GenBank Accession No.L16982) and amino acid sequence (SEQ ID NO:6) of mAb 3E10 V_(H).

FIG. 4 shows the nucleotide and amino acid sequences of mAb 3E10 Vklight chains, 3E1 OVkIII (GenBank Accession No. L34051; SEQ ID NOs:7 and8, for nucleotide and amino acid sequences, respectively) and 3E10VkSER(GenBank Accession No. L16981; SEQ ID NOs:9 and 10, for nucleotide andamino acid sequences, respectively).

DETAILED DESCRIPTION OF THE INVENTION

Before the present methods are described, it is to be understood thatthis invention is not limited to particular compositions, methods, andexperimental conditions described, as such compositions, methods, andconditions may vary. It is also to be understood that the terminologyused herein is for purposes of describing particular embodiments only,and is not intended to be limiting, since the scope of the presentinvention will be limited only in the appended claims.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural references unless the contextclearly dictates otherwise. Thus, for example, references to “themethod” includes one or more methods, and/or steps of the type describedherein which will become apparent to those persons skilled in the artupon reading this disclosure and so forth.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

In accordance with the present invention, there are provided conjugatescontaining a substrate that is capable of being transported by anucleoside transport pathway, and an active agent linked to thesubstrate, wherein the conjugate is transported by the nucleosidetransport pathway. In this way, the conjugate, and thus, the activeagent, is transported into the target cell. In particular embodiments inwhich the substrate is an antibody, the antibody is not the monoclonalantibody 3E10 or a fragment thereof. In certain embodiments, thenucleoside transport pathway includes an equilibrative nucleosidetransporter or a concentrative nucleoside transporter. In embodiments inwhich the nucleoside transport pathway involves an equilibrativenucleoside transporter, such a transporter may be insensitive toinhibition by low concentrations of nitrobenzylmercaptopurine riboside(NBMBR)

“Nucleoside transport pathways” refer to systems of one or moretransport proteins that effect the transport of a substrate across oneor more biological membranes. For example, a nucleoside transportpathway may mediate the step-wise transport of a substrate across theplasma membrane followed by the transport of the substrate across themembrane of an intracellular organelle. The transport proteins ornucleoside transporters responsible for such a step-wise translocationof a substrate across two biological membranes may be the same type ofnucleoside transporter or may be of different types. In certainembodiments, the nucleoside transporter may be an equilibrativenucleoside transporter. In other embodiments, the nucleoside transportermay be a concentrative nucleoside transporter.

A “transport protein” or “transporter” is a protein that has a direct orindirect role in transporting a molecule across a membrane. The termincludes, for example, membrane-bound proteins that recognize asubstrate and effects its entry into, or exit from a cell by acarrier-mediated transporter or by receptor-mediated transport.Transporters may be present on plasma membranes or the membranes ofintracellular oganelles. Thus, transporters facilitate the transport ofmolecules into the cytoplasm or into an intracellular organelle.

Two different families of nucleoside transporters (NTs) have beencharacterized: equilibrative nucleoside transporters and concentrativenucleoside transporters. “Equilibrative nucleoside transporters” or“ENTs” refer to transporters that translocate substrate down thesubstrate's concentration gradient via passive transport or facilitateddiffusion. ENT activity does not require a sodium ion (or other ion)gradient and are therefore termed “Na⁺-independent” transporters. ENTsare categorized into one of two subtypes based on sensitivity toinhibition by nitrobenzylmercaptopurine riboside (NBMBR). One subtype ofENT (equilibrative, sensitive or “es”), is inhibited by ≦1 nM NBMPR,whereas the other subtype (equilibrative, insensitive or “ei”), isunaffected by low concentrations (e.g., <1 μM) of NBMPR.

Four members of the ENT family have been cloned and are termed ENT1,ENT2, ENT3, and ENT4. All 4 transport adenosine but differ from eachother with respect to their ability to transport other nucleosides ornucleobases. ENT1 is an es subtype transporter. Exemplary polynucleotidesequences encoding human ENT1 include GenBank Accession No. U81375 andGenBank Accession No. AAC51103.1 represents the corresponding amino acidsequence. ENT1 is ubiquitously expressed in human and rodent tissues,although expression levels vary between tissues. ENT1 is known totransport a wide range of purine and pyrimidine nucleosides.

ENT2 is an ei subtype transporter. Exemplary polynucleotide sequencesencoding human ENT2 include GenBank Accession No. AF029358 and GenBankAccession No. AAC39526 represents the corresponding amino acid sequence.ENT2 is expressed in a wide range of human and rodent tissues, includingvascular endothelium, heart, brain, placenta, thymus, pancreas,prostate, kidney, and muscle, skeletal muscle, cardiac muscle, blood,skin, and ENT2-expressing cancer cells. ENT2-expressing cancer cellsinclude, for example, certain renal tumor cells, breast tumor cells,prostate cancer cells, colon cancer cells, stomach cancer cells,leukemia cells, lung cancer cells, and ovarian cancer cells. Other typesof ENT-2 expressing cancer cells are known in the art; for example seeLu X et al., Journal of Experimental Therapeutics and Oncology2:200-212, 2002, and Pennycooke M et al., Biochemical and BiophysicalResearch Communications 208, 951-959, 2001. ENT2 exhibits highexpression levels in skeletal muscle. ENT2 is also expressed in themembrane of organelles such as the nucleus. ENT2 is known to transport awide range of purine and pyrimidine nucleosides and nucleobases.

ENT3 is an ei subtype transporter. Exemplary polynucleotide sequencesencoding human ENT3 include GenBank Accession No. NM_(—)018344 andGenBank Accession No. NP_(—)060814 represents the corresponding aminoacid sequence. ENT3 is widely expressed in different tissues and isabundant in placenta. ENT3 appears to be predominantly an intracellularprotein and co-localizes with lysosomal markers in cultured cells. ENT3is known to transport a wide range of purine and pyrimidine nucleosides.

ENT4 is weakly inhibited by NBMPR. Exemplary polynucleotide sequencesencoding human ENT4 include GenBank Accession No. BC047592 and GenBankAccession No. AAH47592 represents the corresponding amino acid sequence.ENT4 is fairly ubiquitously expressed and is abundant in brain, skeletalmuscle, and heart. ENT4 is also substantially expressed in intestine,pancreas, kidney, liver, bone marrow, and lymph node. ENT4 is known totransport a wide range of purine and pyrimidine nucleosides andserotonin.

“Concentrative nucleoside transporters” or “CNTs” refer to a group ofnucleoside transporters that transport nucleosides and nucleosideanalogs by active transport. CNTs employ sodium gradients resulting froma difference in intracellular versus extracellular sodium concentration.This concentration gradient allows an uphill or concentrative transportof substrate across biological membranes. In general, the sodiumconcentration gradient across mammalian cell membranes favors movementof sodium and nucleoside into the cell. CNTs are therefore considered“Na⁺-dependent” transporters. There are currently three cloned membersof the CNT family and differ from each other with respect to substrateselectivity and substrate to sodium ratio.

CNT1 is known to transport pyrimidine nucleosides as well as adenosine,the latter in a high-affinity, low-capacity manner. Transport via CNT1occurs at a ratio of 1:1 sodium-to-nucleoside ratio. Exemplarypolynucleotide sequences encoding human CNT1 include GenBank AccessionNo. U62968 and GenBank Accession No. AAB53839.1 represents thecorresponding amino acid sequence. CNT1 is primarily expressed inepithelial cells of tissues, such as small intestine, kidney, and liver,as well as in many regions of the brain.

CNT2 is known to transport purine nucleosides as well as uridine.Transport via CNT2 occurs at a ratio of 1:1 sodium-to-nucleoside ratio.Exemplary polynucleotide sequences encoding human CNT2 include GenBankAccession No. AF036109 and GenBank Accession No. AAB88539 represents thecorresponding amino acid sequence. CNT2 is expressed in a wide range ofhuman tissues such as the heart, liver, kidney, brain, placenta,pancreas, skeletal muscle, colon, and the small intestine.

CNT3 is known to be broadly selective, transporting purine andpyrimidine nucleosides, as well as various nucleoside analogs. Transportvia CNT3 occurs at a ratio of 2:1 sodium-to-nucleoside ratio. Exemplarypolynucleotide sequences encoding human CNT3 include GenBank AccessionNo. AF305210 and GenBank Accession No. AAG22551 represents thecorresponding amino acid sequence. CNT3 is expressed in tissues such asthe trachea, pancreas, bone marrow, and mammary gland, as well as in lowlevels in the intestine, lung, placenta, prostate, testis, and liver.

A “conjugate” as used herein generally refers to a molecule whichcontains a substrate that is capable of being transported by anucleoside transport pathway linked to an active agent. The conjugate isalso capable of being transported by a nucleoside transporter.

A “substrate” of a transport protein, as used generally herein, is acompound whose uptake into a cell or organelle is facilitated by thetransport protein. Substrates have characteristic kinetic parameters(e.g., V_(max) and K_(m)) for a particular transporter. V_(max) refersto the number of molecules of substrate transported per unit time atsaturating concentration of the substrate. K_(m) refers to theconcentration of the substrate at which the substrate is transported athalf of V_(max). In general, a high value of V_(max) is desirable for asubstrate of a transporter. A low value of K_(m) is desirable fortransport of low concentrations of a compound, and a high value of K_(m)is desirable for transport of high concentrations of a compound. V_(max)is affected both by the intrinsic turnover rate of a transporter(molecules/transporter protein) and transporter density in plasmamembrane that depends on expression level. For these reasons, theintrinsic capacity of a compound to be transported by a particulartransporter is usually expressed as the ratio V_(max) of thecompound/V_(max) of a control compound known to be a substrate for thetransporter.

A “substrate that is capable of being transported by a nucleosidetransport pathway” refers to a molecule compound whose uptake into acell or organelle is facilitated by a nucleoside transport protein ornucleoside transporter. Substrates used in the invention conjugates maybe known substrates of nucleoside transporters or may be identifiedusing methods known in the art and provided herein. Substrates mayinclude a nucleoside, a nucleobase, a nucleotide, a nucleoside analog,an oligonucleotide, a peptide, a polypeptide, an antibody, an antibodyfragment.

The term “nucleobase” refers to purine or pyrimidine bases. Examplesinclude adenine, cytosine, guanine, uracil, and thymine. Nucleobasesinclude modified bases, such as pseudouridine, dihydrouridine, inosine,ribothymidine, 7-methylguanosine (m7G), hypoxanthine, and xanthine.

The term “nucleoside” refers to a purine or pyrimidine base that iscovalently linked to a 5-carbon sugar (i.e., pentose). When the sugar isribose, the nucleoside is a ribonucleoside; when it is 2-deoxyribose,the nucleoside is a deoxyribonucleoside. Exemplary nucleosides includecytidine, uridine, adenosine, guanosine, and thymidine, and thecorresponding deoxyribonucleosides, which form the basis of thenucleotides that form DNA and RNA.

The term “nucleoside analog” as used herein refers to a nucleoside inwhich the base moiety, the sugar moiety or both has been modified. Suchanalogs are generally synthetic and mimic natural nucleosides so thatthey may take the place of a nucleoside in cellular functions. Forexample, nucleosides may be incorporated into DNA or RNA in place of thenatural corresponding nucleoside. Certain nucleoside analogs soincorporated can, for example, prevent further elongation of the nucleicacid chain during synthesis. Many nucleoside analogs have anti-viral oranti-cancer properties. Examples of nucleoside analogs include inosine,deoxyadenosine analogs such as didanosine (2′,3′-dideoxyinosine, ddI)and vidarabine (9-O-D-ribofuranosyladenine), deoxycytidine analogs suchas cytarabine (cytosine arabinoside, emtricitabine, lamivudine(2′,3′-dideoxy-3′-thiacytidine, 3TC), and zalcitabine(2′-3′-dideoxycytidine, ddC), deoxyguanosine analogs such as abacavir,(deoxy-)thymidine analogs such as stavudine(2′-3′-didehydro-2′-3′-dideoxythymidine, d4T) and zidovudine(azidothymidine, or AZT), and deoxyuridine analogs such as idoxuridineand trifluridine.

As used herein, the phrase “active agent” refers to a molecule that hasa biological effect in a cell. In certain embodiments the active agentmay be a nucleic acid, an inorganic molecule, an organic molecule, asmall organic molecule, a drug compound, a peptide, a polypeptide, anantibody, an antibody fragment, a peptidomrnimetic, a lipid, DNA, RNA, aribozyme, hairpin RNA, siRNA (small interfering RNAs) of varyingchemistries, miRNA, an antagomir, a PNA (peptide nucleic acid), an LNA(locked nucleic acids), or a morpholino. In certain embodiments, theactive agent is a polypeptide.

In other embodiments, the active agent is selected from the groupconsisting of α-glucosidase, α-L-iduronidase, α-galactosidase A,arylsulfatase, N-acetylgalactosamine-6-sulfatase or β-galactosidase,iduronate 2-sulfatase, ceramidase, galactocerebrosidase,β-glucuronidase, Heparan N-sulfatase, N-Acetyl-α-glucosaminidase, AcetylCoA-α-glucosaminide N-acetyl transferase, N-acetyl-glucosamine-6sulfatase, Galactose 6-sulfatase, Arylsulfatase A, B, or C,Arylsulfatase A Cerebroside, Ganglioside, Acid βgalactosidase G_(MI)Gaiglioside, Acid β-galactosidase, Hexosaminidase A, Hexosaminidase B,αx-fucosidase, α-N-Acetyl galactosaminidase, Glycoprotein Neuraminidase,Aspartylglucosamine amidase, Acid Lipase, Acid Ceramidase, LysosomalSphingomyelinase and other Sphingomyelinase. In certain embodiments, theactive agent is dystrophin, components of dystrophin-glycoproteincomplex, the laminin-α2 chain, fukutin-related protein, LARGE, fukutin,EMD, LMNA, DMPK, ZNF9, and PABPN1, Glycogen synthase,Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase, or a nucleic acid encoding any of saidproteins.

In certain embodiments, the substrate is an antibody or fragmentthereof. For example, the antibody or fragment thereof may bindnucleosides, nucleotides, nucleobases, oligonucleotides,polynucleotides, or nucleic acid. In certain embodiments in which thesubstrate is an antibody, it is not the 3E10 antibody or the antibodyproduced by the hybridoma having the ATCC accession number PTA 2439.

In certain embodiments the substrate portion of the conjugate may be aDNA-binding autoantibody. Examples of such DNA-binding autoantibodiesinclude an antibody having the binding specificity of the antibody asproduced by the hybridoma having ATCC accession number PTA 2439,antibody mAb 3E10, and variants and/or functional fragments thereof. Thenucleotide and amino acid sequences for the variable region of the heavychain of mAb 3E10 are provided in FIG. 3. The nucleotide and amino acidsequences for the variable region of the light chains of mAb 3EI 0 areprovided in FIG. 4. In particular, the light chain designated VkIIIcontains the DNA binding capability for mAb 3E10. Thus, VkIII is thepreferred light chain for 3E10 to be used in the methods of the presentinvention.

Although antibodies that penetrate living cells are frequently toxic orinjurious and may explain some of the pathologic manifestations of theautoimmune diseases in which they are found, antibody mAb 3E10, incontrast, shows no harm to cells that it penetrates in tissue culture.Moreover, studies in vitro have shown that mAb 3E10 and scFv fragmentsof mAb 3E10 can transport relatively large proteins, such as catalase,into the nucleus of cells in tissue culture. Moreover, mAb 3E10 orfragments thereof (e.g., Fv) should not generate significantinflammation in vivo which could hinder therapeutic efficacy of abiologically active molecule conjugated thereto. Monoclonal antibody3E10 is produced by the hybridoma 3E10 placed permanently on depositwith the American Type Culture Collection, 10801 University Blvd.,Manassas, Va. 20110-2209, USA, on Aug. 31, 2000, according to the termsof the Budapest Treaty under ATCC accession number PTA-2439 and are thusmaintained and made available according to the terms of the BudapestTreaty. Availability of such strains is not to be construed as a licenseto practice the invention in contravention of the rights granted underthe authority of any government in accordance with its patent laws.

As used herein, “specific binding” refers to antibody binding to apredetermined antigen. Typically, the antibody binds with an affinitycorresponding to a K_(D) of about 10⁻⁸ M or less, and binds to thepredetermined antigen with an affinity (as expressed by K_(D)) that isat least 10 fold less, and preferably at least 100 fold less than itsaffinity for binding to a non-specific antigen (e.g., BSA, casein) otherthan the predetermined antigen or a closely-related antigen.Alternatively, the antibody can bind with an affinity corresponding to aK_(A) of about 10⁶ M⁻¹, or about 10⁷ M⁻¹, or about 10⁸ M⁻¹, or 10⁹ M⁻¹or higher, and binds to the predetermined antigen with an affinity (asexpressed by K_(A)) that is at least 10 fold higher, and preferably atleast 100 fold higher than its affinity for binding to a non-specificantigen (e.g., BSA, casein) other than the predetermined antigen or aclosely-related antigen. In some embodiments the antibody variant orfunctional fragment will have the same K_(A) or K_(D) as an antibodyproduced by the hybridoma having ATCC accession number PTA 2439. Incertain embodiments, the antibody variant or functional fragment willhave the same K_(A) or K_(D) as mAb 3E10.

The term “k_(d)” (sec⁻¹), as used herein, is intended to refer to thedissociation rate constant of a particular antibody-antigen interaction.This value is also referred to as the off value.

The term “k_(a)” (M⁻¹sec⁻¹), as used herein, is intended to refer to theassociation rate constant of a particular antibody-antigen interaction.The term “K_(A)” (M), as used herein, is intended to refer to theassociation equilibrium constant of a particular antibody-antigeninteraction.

The term “K_(D)” (M⁻¹), as used herein, is intended to refer to thedissociation equilibrium constant of a particular antibody-antigeninteraction.

Naturally occurring antibodies are generally tetramers containing twolight chains and two heavy chains. Experimentally, antibodies can becleaved with the proteolytic enzyme papain, which causes each of theheavy chains to break, producing three separate subunits. The two unitsthat consist of a light chain and a fragment of the heavy chainapproximately equal in mass to the light chain are called the Fabfragments (i.e., the “antigen binding” fragments). The third unit,consisting of two equal segments of the heavy chain, is called the Fcfragment. The Fc fragment is typically not involved in antigen-antibodybinding, but is important in later processes involved in ridding thebody of the antigen.

As used herein, the phrase “functional fragments of an antibody havingthe binding specificity of the antibody as produced by the hybridomahaving ATCC accession number PTA 2439” refers to a fragment that retainsthe same cell penetration characteristics and binding specificity as mAb3E10. Thus, in certain embodiments, a functional fragment of an antibodyhaving the binding specificity of the antibody as produced by thehybridoma having ATCC accession number PTA 2439 or antibody mAb 3E10 isused in the conjugate. In some embodiments, the functional fragment usedin the conjugate is selected from the group consisting of Fab, F(ab′)₂,Fv, and single chain Fv (scFv) fragments. In certain embodiments thefunctional fragment is an Fv fragments or an scFv fragment. In oneexample, the functional fragment includes at least the antigen-bindingportion of mAb 3E10. In another example, the functional fragments is anscFv fragment including the variable region of the heavy chain (VH) andvariable region of the kappa light chain (Vκ) of mAb 3E10. For increasedexpression in the polynucleotide from which the scFv is expressed, thenucleic acids encoding the chains of mAb E310 are placed in reverseorder with the Vκc cDNA being placed 5′ of VH. In addition, one or moretags known in the art, preferably peptide (e.g., myc or His₆), may beincorporated into a conjugate to facilitate in vitro purification orhistological localization of the conjugate. In some embodiments, the amyc tag and a His₆ tag are added to the C-terminus of VH.

As readily recognized by those of skill in the art, altered antibodies(e.g., chimeric, humanized, CDR-grafted, bifunctional, antibodypolypeptide dimers (i.e., an association of two polypeptide chaincomponents of an antibody, e.g., one arm of an antibody including aheavy chain and a light chain, or an Fab fragment including V_(L),V_(H), C_(L) and C_(H)1 antibody domains, or an Fv fragment comprising aV_(L) domain and a V_(H) domain), single chain antibodies (e.g., an scFv(i.e., single chain Fv) fragment including a V_(L) domain linked to aV_(H) domain by a linker, and the like) can also be produced by methodswell known in the art. Such antibodies can also be produced byhybridoma, chemical synthesis or recombinant methods described, forexample, in (Sambrook et al., Molecular Cloning: A Laboratory Manual 2dEd. (Cold Spring Harbor Laboratory, 1989); incorporated herein byreference and Harlow and Lane, Antibodies. A Laboratory Manual (ColdSpring Harbor Laboratory 1988), which is incorporated herein byreference). Both anti-peptide and anti-conjugate antibodies can be used(see, for example, Bahouth et al., Trends Pharmacol. Sci. 12:338 (1991);Ausubel et al., Current Protocols in Molecular Biology (John Wiley andSons, NY 1989) which are incorporated herein by reference). See inparticular, FIGS. 2 and 3 for specific nucleotide and amino acidsequences of the illustrative antibody of the invention designated mAb3E10.

For example, antibodies may be humanized by replacing sequences of theFv variable region which are not directly involved in antigen bindingwith equivalent sequences from human Fv variable regions. Generalreviews of humanized chimeric antibodies are provided by Morrison etal., (Science 229:1202-1207, 1985) and by Oi et al. (BioTechniques4:214, 1986). Those methods include isolating, manipulating, andexpressing the nucleic acid sequences that encode all or part ofimmunoglobulin Fv variable regions from at least one of a heavy or lightchain. Sources of such nucleic acid are well known to those skilled inthe art and, for example, may be obtained from for example, an antibodyproducing hybridoma. The recombinant DNA encoding the humanized orchimeric antibody, or fragment thereof, can then be cloned into anappropriate expression vector. Humanized antibodies can alternatively beproduced by CDR substitution U.S. Pat. No. 5,225,539; Jones (1986)Nature 321:552-525; Verhoeyan et al. 1988 Science 239:1534; and Beidler(1988) J. Immunol. 141:4053-4060. Thus, in certain embodiments, theantibody used in the conjugate is a humanized or CDR-grafted form of anantibody produced by the hybridoma having ATCC accession number PTA2439. In other embodiments the antibody is a humanized or CDR-graftedform of antibody mAb 3E10. For example, the CDR regions of theillustrative antibody of the invention, as shown in FIGS. 2 and 3, caninclude amino acid substitutions such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or10 amino acid differences from those shown in the figures. In someinstances, there are anywhere from 1-5 amino acid differences.

As used herein, reference to variants of an antibody having the bindingspecificity of an antibody as produced by the hybridoma having ATCCaccession number PTA 2439″ includes variants retaining the same cellpenetration characteristics and binding specificity as mAb 3E10, as wellas variants modified by mutation to improve the utility thereof (e.g.,improved ability to target specific cell types, improved ability topenetrate the cell membrane, improved ability to localize to thecellular DNA, and the like). Such variants include those wherein one ormore conservative substitutions are introduced into the heavy chain, thelight chain and/or the constant region(s) of the antibody. In someembodiments the variant has a light chain having an amino acid sequenceat least 80% or at least 90% or at least 95% identical to the amino acidsequence set forth in SEQ ID NO:8. In other embodiments, the variant hasa heavy chain having an amino acid sequence at least 80% or at least 90%or at least 95% identical to the amino acid sequence set forth in SEQ IDNO:6. Further, the invention includes antibodies that are encoded bynucleic acid sequences that hybridize under stringent conditions to the3E10 variable region coding sequence (e.g., SEQ ID NO:5 and/or SEQ IDNO:7) or encode amino acid sequences at least 80% or at least 90% or atleast 95% identical to the amino acid sequence set forth in SEQ ID NO:6or SEQ ID NO:8.

Such variants include those wherein one or more substitutions areintroduced into the heavy chain nucleotide sequence, the light chainnucleotide sequence and/or the constant region(s) of the antibody. Insome embodiments the variant has a light chain having a nucleotidesequence at least 80% or at least 90% or at least 95% identical to thenucleotide sequence set forth in SEQ ID NO:7. In other embodiments, thevariant has a heavy chain having a nucleotide sequence at least 80% orat least 90% or at least 95% identical to the nucleotide sequence setforth in SEQ ID NO:5.

One exemplary variant contemplated for use in the practice of thepresent invention is an mAb 3E10 VH variant involving a single change ofthe aspartic acid residue at position 31 to asparagine (i.e., mAb3E10-31). The preparation of this variant and further variants and ademonstration of its cell penetration ability is described in U.S. Pat.No. 7,189,396. This particular mAb 3E10 variant is especially wellsuited for delivery of biological molecules to kidney and brain cells.Other 3E10 variants and/or functional fragments thereof may be used toprovide targeting of biologically active molecules. A wide variety ofvariants and/or functional fragments thereof are possible provided thatthey exhibit substantially the same cell penetration characteristics asmAb 3E10 or mAb 3E10-31 after conjugation to a selected biologicallyactive molecule.

In other embodiments, novel substrates can be generated that target oneor more specific nucleoside transporter. Such novel substrates could begenerated using, for example molecular modeling and protein mimeticmethodologies based on structures of known substrates.

Conjugates in which the substrate and active agent are polypeptides(i.e., protein conjugates) can be designed to place the active agent atthe amino or carboxy terminus the substrate using well-known recombinantDNA methodologies. Such conjugates can be expressed in a host cell as afusion protein. Alternatively, the substrate and active agent can bechemically linked by a peptide bond or by a chemical or peptide linkermolecule of the type well known in the art. The linker may be one ormore tags (e.g., myc or His₆ (SEQ ID NO:12)) or may be one or morerepeats of the known linker sequence GGGGS (SEQ ID NO:11). Additionalpeptide linkers are known in the art. The skilled artisan will recognizethat the linker sequence may be varied depending on the polypeptide tobe linked to the antibody.

Vectors suitable for use in preparation of protein conjugates includethose selected from baculovirus, phage, plasmid, phagemid, cosmid,fosmid, bacterial artificial chromosome, viral DNA, Pl-based artificialchromosome, yeast plasmid, and yeast artificial chromosome. For example,the viral DNA vector can be selected from vaccinia, adenovirus, foul poxvirus, pseudorabies and a derivative of SV40. Suitable bacterial vectorsfor use in practice of the invention methods include pQE70, pQE60,pQE-9, pBLUESCRIPT SK, pBLUESCRIPT KS, pTRC99a, pKK223-3, pDR540, PACand pRIT2T. Suitable eukaryotic vectors for use in practice of theinvention methods include pWLNEO, pXTI, pSG5, pSVK3, pBPV, pMSG, andpSVLSV40. Suitable eukaryotic vectors for use in practice of theinvention methods include pWLNEO, pXTI, pSG5, pSVK3, pBPV, pMSG, andpSVLSV40.

Those of skill in the art can select a suitable regulatory region to beincluded in such a vector, for example from lacI, lacZ, T3, T7, apt,lambda PR, PL, trp, CMV immediate early, HSV thymidine kinase, early andlate SV40, retroviral LTR, and mouse metallothionein-I regulatoryregions.

Host cells in which the vectors containing the polynucleotides encodingthe protein conjugates can be expressed include a bacterial cell, aeukaryotic cell, a yeast cell, an insect cell, or a plant cell. Forexample, E. coli, Bacillus, Streptomyces, Pichia pastoris, Salmonellatyphimurium, Drosophila S2, Spodoptera SJ9, CHO, COS (e.g. COS-7), orBowes melanoma cells are all suitable host cells for use in practice ofthe invention methods.

Conjugates in which the substrate is a polypeptide and the active agentis a small molecule or drug compound may be generated using methodsknown in the art. For example, methods for attaching a drug or othersmall molecule pharmaceutical to protein include bifunctional chemicallinkers such as N-succinimidyl (4-iodoacetyl)-aminobenzoate;sulfosuccinimidyl(4-iodoacetyl)-aminobenzoate;4-succinimidyl-oxycarbonyl-α-(2-pyridyldithio) toluene;sulfosuccinimidyl-6-[α-methyl-α-(pyridyldithiol)-toluamido]hexanoate;N-succinimidyl-3-(2-pyridyldithio)-proprionate;succinimidyl-6-[3(-(-2-pyridyldithio)-proprionamido]hexanoate;sulfosuccinimidyl-6-[3(-(-2-pyridyldithio)-propionamido]hexanoate;3-(2-pyridyldithio)-propionyl hydrazide, Ellman's reagent,dichlorotriazinic acid, S-(2-thiopyridyl)-L-cysteine, and the like.Further bifunctional linking molecules are disclosed in U.S. Pat. Nos.5,349,066; 5,618,528; 4,569,789; 4,952,394; and 5,137,877, each of whichis incorporated herein by reference in its entirety.

According to a further embodiment of the invention, there are providedmethods of screening a conjugate for transport by a nucleoside transportpathway in which the method includes, contacting a cell expressing thenucleoside transport pathway, with a conjugate under suitable conditionsfor transport to occur; and determining whether the conjugate istransported into the cell by the nucleoside transport pathway. Incertain embodiments, the determining step includes comparing the amountof conjugate transported into a cell expressing the nucleoside transportsystem to the amount of conjugate transported into a control cell notexpressing the nucleoside transport system, wherein an increase intransport of conjugate of the cell expressing the nucleoside transportpathway as compared to the control cell indicates transport is by thatnucleoside transport pathway.

In particular embodiments of the above screening method, the nucleosidetransport pathway includes an equilibrative nucleoside transporter or aconcentrative nucleoside transporter. In some embodiments, theequilibrative nucleoside transporter is selected from the groupconsisting of ENT1, ENT2, ENT3, and ENT4. In certain embodiments, theequilibrative nucleoside transporter is insensitive to lowconcentrations of nitrobenzylmercaptopurine riboside (NBMBR). Inparticular embodiments, the cell is transfected with DNA encoding thenucleoside transporter. Such embodiments may further include a step inwhich the amount of conjugate transported into the cell transfected withDNA encoding the nucleoside transporter is compared to the amount ofconjugate transported into a control cell not transfected with thenucleoside transporter, wherein an increase in transport of conjugate ofthe transfected cell as compared to the control cell indicates transportis by the nucleoside transporter.

Screening methods may further include compounds that inhibit nucleosidetransport activity. For example, NBMPR, dilazep, dipyridamole, anddraflazine are inhibitors of certain es nucleoside transporters (e.g.,ENT1). Thus, in certain embodiments low concentrations of NBMPR may beincluded.

In certain embodiments, the conjugate may further contain a detectablelabel. Such labels are known in the art and include radio-isotopes andfluorescent labels.

Conjugates can be screened directly for their capacity to be transportedby nucleoside transport pathways. The screening is typically performedon cells expressing the nucleoside transport pathway. In some methods,the cells are transfected with DNA encoding the a particular nucleosidetransporter (NT). In other methods, cells expressing an endogenous NTare used. Cells may express endogenous CNTs and/or an ENTs. In somemethods, an ENT is the only NT expressed. In other methods, cellsexpressing both ENT1 and ENT2 are used.

Internalization of a compound evidencing passage through transporterscan be detected by detecting a signal from within a cell from any of avariety of reporters. The reporter can be as simple as a label such as afluorophore, a chromophore, a radioisotope. Confocal imagining can alsobe used to detect internalization of a label as it provides sufficientspatial resolution to distinguish between fluorescence on a cell surfaceand fluorescence within a cell; alternatively, confocal imaging can beused to track the movement of compounds over time. In another approach,internalization of a compound is detected using a reporter that is asubstrate for an enzyme expressed within a cell. Once the complex isinternalized, the substrate is metabolized by the enzyme and generatesan optical signal or radioactive decay that is indicative of uptake.Light emission can be monitored by commercial PMT-based instruments orby CCD-based imaging systems. In addition, assay methods utilizing LCMSdetection of the transported compounds or electrophysiological signalsindicative of transport activity are also employed.

In some methods, multiple conjugates are screened simultaneously and theidentity of each agent or conjugate moiety is tracked using labelslinked to the conjugates. In some methods, the screening can beperformed in a competition format in which an a conjugate under test anda known substrate of the nucleoside transporter are applied to the samecells. Typically, the conjugate and known substrate are differentiallylabeled in such assays. Alternatively, the known substrate may belabeled and parallel measurements of uptake of labeled substrate in thepresence and absence test conjugate may be compared.

In such comparative assays, the Vmax of a conjugate can be compared withthat of known substrate. If a conjugate has a Vmax of at least 1%,preferably at least 5%, more preferably at least 10%, even morepreferably at least 20%, and most preferably at least 50% of knownsubstrate for the transporter then the conjugate can be considered to bea substrate for that NT.

Nucleic Acid Therapeutics

In certain embodiments, the compositions herein may be used to delivernucleic acids, or analogs thereof, to a targeted tissue or cell type.For example, protein expression can be specifically down-regulated usingoligonucleotides such, for example, as antisense, locked nucleic acids(LNA), peptide nucleic acids (PNA), morpholino nucleic acids(Morpholinos) and small interfering RNAs (siRNA) of various chemistries.Alternatively, expression constructs may be delivered to cells, toinduce expression of a desired gene product.

Nucleic acids which modulate the expression of a certain gene or geneproduct may be administered. As used herein, “a nucleic acid thatmodulates expression of . . . ” encompasses nucleic acids thatup-regulate and down-regulate the expression of the given gene or geneproduct. For example, an expression construct can expresses the gene ofinterest and cause up-regulation. Alternatively, a nucleic acid thatcauses down-regulation can be, for example, a siRNA, a construct thatexpresses an antisense RNA (such as a short hairpin RNA), or a ribozyme.

Nucleic acid therapeutics, such as oligonucleotides directed againstintracellular targets (mRNA or protein), are powerful therapeuticagents. Examples of oligonucleotide therapeutic agents include:antisense oligonucleotides, which are short, single-stranded DNAs andRNAs that bind to complementary mRNA and inhibit translation or induceRNaseH-mediated degradation of the transcript; siRNA oligonucleotides,which are short, double-stranded RNAs that activate the RNA interference(RNAi) pathway leading to mRNA degradation; ribozymes, which areoligonucleotide-based endonucleases that are designed to cleave specificmRNA transcripts; and nucleic acid aptamers and decoys, which arenon-naturally occurring oligonucleotides that bind to and block proteintargets in a manner analogous to small molecule drugs.

As used herein, the term “nucleic acid” refers to polynucleotides suchas deoxyribonucleic acid (DNA), and, where appropriate, ribonucleic acid(RNA). The term should also be understood to include, as appropriate tothe context or as applicable to the embodiment being described, bothsingle-stranded polynucleotides (such as antisense) and double-strandedpolynucleotides (such as siRNAs). The term “nucleic acid” encompasses,for example, DNA molecules, RNA molecules, RNAi molecules and siRNAmolecules, microRNA molecules, native RNA molecules, ribozyme RNAmolecules, aptamers, plasmids, cDNA molecules, anti-sense DNA strands,and oligonucleotides. It further encompasses DNA molecules (in the formof plasmids, cDNA, linear DNA, oligos or anti-sense DNA stands) RNAmolecules (in the form of siRNA, mRNA, shRNA, ribozymes, RNAi,)aptamers, proteins (antibodies, polypeptides, peptides or fragment ofproteins), nucleic acids conjugated to other compounds (such asfluorescent dyes, small molecular inhibitors of specific proteins).There are a number of nucleic acid-based therapeutic agents in variousstages of development at this time. Among them are antisense agents,aptamers, ribozymes, and small interfering RNAs (siRNAs). M. Faria, H.Ulrich, Curr. Cancer Drug Targets 2002, 2: 355-368.

Antisense agents may be the most advanced class of these agents, withone product (fomivirsen) on the market for the treatment of CMVretinitis, another (alicaforsen) in advanced clinical trials fortreatment of Crohn's disease, and Genasense™ (oblimersen sodium),Affinitac™, and Oncomyc-NG™ in clinical trials for treatment of cancer.Antisense agents are typically short, chemically-modifiedoligonucleotide chains that hybridize to a specific complementary areaof a targeted mRNA. The resulting mRNA duplex is recognized and degradedby RNAse H, thereby destroying the mRNA. Because the mRNA instructionsfail to reach the ribosome, production of the protein encoded by thetargeted mRNA is prevented. By inhibiting the production of proteinsinvolved in disease, antisense drugs can produce a therapeutic benefit.

An aptamer is a DNA or RNA molecule that has been selected from a randomor biased pool of oligonucleic acids, based on its ability to bind to atarget molecule. Aptamers can be selected which bind nucleic acids,proteins, small organic compounds and specific cell surfaces, andseveral have been developed which bind to proteins which are associatedwith disease states. Aptamers are in general more easily manufacturedand are more amenable to chemical modification than are antibodies, andthey can be “evolved” for tighter binding to the target by an iterativeprocess of random modification and affinity-based selection. The evolvedaptamers often have antibody-like specificities, and are thereforeexpected to have utility in those applications, such as therapeutics andin vitro and in vivo diagnostics, where antibodies have already proveduseful. At least one product, Macugen™ (pegaptanib sodium, a PEGylatedaptamer with high affinity for VEGF), is in advanced clinical trials forthe treatment of age-related macular degeneration.

Ribozymes, or RNA enzymes, are RNA molecules that can catalyze achemical reaction. All ribozymes found naturally so far catalyze thecleavage of RNA. They range in size from the large “hammerhead”ribozymes to the so-called “minizymes” which are synthetic constructscontaining the minimal structures needed for activity. DNA-based enzymes(deoxyribozymes, or DNAzymes) having similar properties have also beenprepared. The ability of ribozymes to recognize and cut specific mRNAmolecules gives them considerable potential as therapeutic agents. Aribozyme designed to catalyze the cleavage of a specific mRNA would beuseful as a therapeutic agent in the same way that a complimentaryantisense nucleic acid would be, but with the advantage that a singleribozyme molecule can destroy many copies of the mRNA. A syntheticribozyme (Angiozyme™) that cleaves the mRNA encoding a VEGF receptorsubtype is currently in clinical trials for treatment of cancer.

RNA interference (RNAi) is the phenomenon of gene-specificpost-transcriptional silencing by double-stranded RNA oligomers(Elbashir et al. Nature 2001, 411: 494-498; Caplen et al., Proc. Natl.Acad. Sci. U.S.A. 2001, 98: 9742-9747). Small inhibitory RNAs (siRNAs),like antisense oligonucleic acids and ribozymes, have the potential toserve as therapeutic agents by reducing the expression of harmfulproteins. The double-stranded siRNA is recognized by a protein complex(the RNA induced silencing complex), which strips away one of thestrands, facilitates hybridization of the remaining strand to the targetmRNA, and then cleaves the target strand. DNA-based vectors capable ofgenerating siRNA within cells are also of interest for the same reason,as are short hairpin RNAs that are efficiently processed to form siRNAswithin cells. siRNAs capable of specifically targeting endogenously andexogenously expressed genes have been described; see for examplePaddison et al., Proc. Natl. Acad. Sci. U.S.A., 2002, 99: 1443-1448;Paddison et al., Genes & Dev. 2002, 16: 948-958; Sui et al. Proc. Natl.Acad. Sci. U.S.A. 2002, 8: 5515-5520; and Brummelkamp et al., Science2002, 296: 550-553.

The term “nucleic acid-based therapeutic agent” as used herein refers tothree classes of compounds. The term also includes pharmaceuticallyacceptable salts, esters, prodrugs, codrugs, and protected forms of thecompounds, analogs and derivatives described below. The first class,referred to herein collectively as “antisense nucleic acids,” comprisesnucleic acids, preferably oligomers of about 50 monomer units or fewer,which have the ability to hybridize in a sequence-specific manner to atargeted single-stranded RNA or DNA molecule. Members of this classinclude ordinary DNA and RNA oligomers, DNA and RNA having modifiedbackbones, including but not limited to phosphorothioates,phosphorodithioates, methylphosphonates, and peptide nucleic acids,2′-deoxy derivatives, and nucleic acid oligomers that feature chemicallymodified purine and pyrimidine bases, or have been lipophilicallymodified and/or PEGylated to modify their pharmacodynamics. Oligomersthat serve as precursors for such agents, such as hairpin RNAs that areconverted to siRNAs within cells, are also considered to be within thisclass.

The second class of nucleic acid-based therapeutic agents is aptamers.Aptamers comprises nucleic acids, preferably oligomers of about 50monomer units or fewer, which have the ability to bind with structuralspecificity to a non-oligonucleotide target molecule, or to anoligonucleotide in a manner other than through sequence-specifichybridization. Members of this class include DNA and RNA aptamers, andmodifications thereof including but not limited to mirror-image DNA andRNA (“Spiegelmers”), peptide nucleic acids, and nucleic acid oligomersthat have otherwise been chemically modified as described above. Again,any of these species may also feature chemically modified purines andpyrimidines or may be lipophilically modified and/or PEGylated. See M.Rimmele, Chembiochem. 2003, 4: 963-71 and A. Vater and S. Klussmann,Curr. Opin. Drug Discov. Devel. 2003, 6: 253-61 for recent reviews ofaptamer technology. It will be appreciated that many members of thissecond class will, in addition to their structure-specific affinity forthe target molecule, have sequence-specific affinity for a putative DNAor RNA sequence.

The third class of nucleic acid-based therapeutic agents, referred toherein as “nucleic acid enzymes,” comprises nucleic acids that arecapable of recognizing and catalyzing the cleavage of target RNAmolecules, in a sequence-specific manner. The class includes hammerheadribozymes, minimized hammerheads (“minizymes”), ‘10-23’ deoxyribozymes(“DNAzymes”), and the like. As with antisense and aptamer molecules, theclass includes catalytic species that have been chemically modified.

The term “pharmaceutically acceptable salts” refers to physiologicallyand pharmaceutically acceptable salts of the compounds of the invention,e.g., salts that retain the desired biological activity of the parentcompound and do not impart undesired toxicological effects thereto.

A “protein coding sequence” or a sequence that “encodes” a particularpolypeptide or peptide, is a nucleic acid sequence that is transcribed(in the case of DNA) and is translated (in the case of mRNA) into apolypeptide in vitro or in vivo when placed under the control ofappropriate regulatory sequences. The boundaries of the coding sequenceare determined by a start codon at the 5′ (amino) terminus and atranslation stop codon at the 3′ (carboxyl) terminus. A coding sequencecan include, but is not limited to, cDNA from prokaryotic or eukaryoticmRNA, genomic DNA sequences from prokaryotic or eukaryotic DNA, and evensynthetic DNA sequences. A transcription termination sequence willusually be located 3′ to the coding sequence.

As used herein, the term “RNAi construct” is a generic term includingsiRNA, hairpin RNA, and other RNA species which can be cleaved in vivoto form siRNAs. RNAi constructs herein also include expression vectors(also referred to as RNAi expression vectors) capable of giving rise totranscripts which form dsRNAs or hairpin RNAs in cells, and/ortranscripts which can be converted into siRNAs in vivo.

As used herein, the term “vector” refers to a nucleic acid moleculecapable of transporting another nucleic acid to which it has beenlinked. One type of vector is a genomic integrated vector, or“integrated vector,” which can become integrated into the chromosomalDNA of the host cell. Another type of vector is an episomal vector,e.g., a nucleic acid capable of extra-chromosomal replication. Vectorscapable of directing the expression of genes to which they areoperatively linked are referred to herein as “expression vectors.” Inthe present specification, “plasmid” and “vector” are usedinterchangeably unless otherwise clear from the context. In theexpression vectors, regulatory elements controlling transcription can begenerally derived from mammalian, microbial, viral or insect genes. Theability to replicate in a host, usually conferred by an origin ofreplication, and a selection gene to facilitate recognition oftransformants may additionally be incorporated. Vectors derived fromviruses, such as retroviruses, adenoviruses, and the like, may beemployed.

In one embodiment, the present disclosure relates to the use ofantisense nucleic acid to decrease expression of a targeteddisease-related protein. Such an antisense nucleic acid can bedelivered, for example, as an expression plasmid which, when transcribedin the cell, produces RNA which is complementary to at least a uniqueportion of the cellular mRNA which encodes the targeted disease-relatedprotein. Alternatively, the construct is an oligonucleotide which isgenerated ex vivo and which, when introduced into the cell causesinhibition of expression by hybridizing with the mRNA and/or genomicsequences encoding the targeted disease-related protein. Sucholigonucleotides are optionally modified so as to be resistant toendogenous exonucleases and/or endonucleases. Exemplary nucleic acidmolecules for use as antisense oligonucleotides are phosphoramidate,phosphothioate and methylphosphonate analogs of DNA (see for exampleU.S. Pat. Nos. 5,176,996; 5,264,564; and 5,256,775). General approachesto constructing oligomers useful in nucleic acid therapy have beenreviewed, for example, by van der Krol et al., (1988) Biotechniques 6:958-976; and Stein et al., (1988) Cancer Res 48: 2659-2668.

In other embodiments, this application relates to the use of RNAinterference (RNAi) to effect knockdown of the targeted gene. RNAiconstructs comprise double stranded RNA that can specifically blockexpression of a target gene. RNAi constructs can comprise either longstretches of dsRNA identical or substantially identical to the targetnucleic acid sequence, or short stretches of dsRNA identical orsubstantially identical to only a region of the target nucleic acidsequence.

Optionally, the RNAi constructs may contain a nucleotide sequence thathybridizes under physiologic conditions of the cell to the nucleotidesequence of at least a portion of the mRNA transcript for the gene to beinhibited (the “target” gene). The double-stranded RNA need only besufficiently similar to natural RNA that it has the ability to induceRNAi. Thus, the invention contemplates embodiments that are tolerant ofsequence variations that might be expected due to genetic mutation,polymorphic sites, or evolutionary divergence in a targeted sequence.The number of tolerated nucleotide mismatches between the targetsequence and the RNAi construct sequence may be as high as 1 in 5 basepairs, but is preferably no higher than 1 in 10 base pairs. Mismatchesin the center of the siRNA duplex are most critical and may essentiallyabolish cleavage of the target RNA. In contrast, nucleotides at the 3′end of the siRNA strand that is complementary to the target RNA do notsignificantly contribute to specificity of the target recognition.Sequence identity may be optimized by sequence comparison and alignmentalgorithms known in the art (see Gribskov and Devereux, SequenceAnalysis Primer, Stockton Press, 1991, and references cited therein) andcalculating the percent difference between the nucleotide sequences by,for example, the Smith-Waterman algorithm as implemented in the BESTFITsoftware program using default parameters (e.g., University of WisconsinGenetic Computing Group). Between 90% and 100% sequence identity betweenthe inhibitory RNA and the portion of the target gene is preferred.Alternatively, the duplex region of the RNA may be defined functionallyas a nucleotide sequence that is capable of detectably hybridizing withthe target gene transcript after hybridization for 12 to 16 hours at50.degree. C. to 70.degree. C. in 400 mM NaCl, 40 mM PIPES pH 6.4, and1.0 mM EDTA, followed by washing.

The double-stranded structure may be formed by a singleself-complementary RNA strand or two complementary RNA strands.Formation of the dsRNA may be initiated inside or outside of the cell.The RNA may be introduced in an amount which allows delivery of at leastone copy per cell. Higher doses (e.g., at least 5, 10, 100, 500 or 1000copies per cell) of double-stranded material may yield more effectiveinhibition, while lower doses may also be useful for specificapplications.

The subject RNAi constructs can be “small interfering RNAs” or “siRNAs.”These nucleic acids are less than about 50, and preferably around 19-30nucleotides in length, more preferably 21-23 nucleotides in length. ThesiRNAs are thought to recruit nuclease complexes and guide the complexesto the target mRNA by pairing to the specific sequences. As a result,the target mRNA is degraded by the nucleases in the protein complex. Ina particular embodiment, the 21-23 nucleotides siRNA molecules comprisea 3′ hydroxyl group. In certain embodiments, the siRNA constructs can begenerated by processing of longer double-stranded RNAs, for example, inthe presence of the enzyme DICER. In one embodiment, the Drosophila invitro system is used. In this embodiment, dsRNA is combined with asoluble extract derived from Drosophila embryo, thereby producing acombination. The combination is maintained under conditions in which thedsRNA is processed to RNA molecules of about 21 to about 23 nucleotides.The siRNA molecules can be purified using a number of techniques knownto those of skill in the art, such as gel electrophoresis.Alternatively, non-denaturing methods, such as column chromatography,size exclusion chromatography, glycerol gradient centrifugation, andaffinity purification can be used to purify siRNAs.

Production of RNAi constructs can be carried out by chemical syntheticmethods or by recombinant nucleic acid techniques. Endogenous RNApolymerase of the treated cell may mediate transcription in vivo, orcloned RNA polymerase can be used for transcription in vitro. The RNAiconstructs may include modifications to either the phosphate-sugarbackbone or the nucleoside, e.g., to reduce susceptibility to cellularnucleases, improve bioavailability, improve formulation characteristics,and/or change other pharmacokinetic properties. For example, thephosphodiester linkages of natural RNA may be modified to include atleast one nitrogen or sulfur heteroatom. Modifications in RNA structuremay be tailored to allow specific genetic inhibition while avoiding ageneral response to dsRNA. Likewise, bases may be modified to block theactivity of adenosine deaminase. The RNAi construct may be producedenzymatically or by partial/total organic synthesis, any modifiedribonucleotide can be introduced by in vitro enzymatic or organicsynthesis. Methods of chemically modifying RNA molecules can be adaptedfor modifying RNAi constructs (see, e.g., Heidenreich et al. (1997)Nucleic Acids Res. 25: 776-780; Wilson et al. (1994) J. Mol. Recog. 7:89-98; Chen et al. (1995) Nucleic Acids Res. 23: 2661-2668; Hirschbeinet al. (1997) Antisense Nucleic Acid Drug, Dev. 7: 55-61). For example,the backbone of an RNAi construct can be modified withphosphorothioates, phosphoramidate, phosphodithioates, chimericmethylphosphonate-phosphodie-sters, peptide nucleic acids,5-propynyl-pyrimidine containing oligomers or sugar modifications (e.g.,2′-substituted or 2′-deoxy ribonucleosides, .alpha.-configurations,etc.)

In some embodiments, at least one strand of the siRNA molecules may havea 3′ overhang from about 1 to about 6 nucleotides in length. Preferably,the 3′ overhangs are 1-3 nucleotides in length. In certain embodiments,one strand has a 3′ overhang and the other strand is blunt-ended or alsohas an overhang. The length of the overhangs may be the same ordifferent for each strand. In order to further enhance the stability ofthe siRNA, the 3′ overhangs can be stabilized against degradation. Inone embodiment, the RNA is stabilized by including purine nucleotides,such as adenosine or guanosine nucleotides. Alternatively, substitutionof pyrimidine nucleotides by modified analogues, e.g., substitution ofuridine nucleotide 3′ overhangs by 2′-deoxythymidine, may be toleratedwithout reducing the effectiveness of the RNAi. The absence of a 2′hydroxyl significantly enhances the nuclease resistance of the overhangin tissue culture medium, and may be also beneficial in vivo.

The RNAi construct can also be in the form of a long double-strandedRNA, which is digested intracellularly to produce a siRNA sequencewithin the cell. Alternatively, the RNAi construct may be in the form ofa hairpin RNA. It is known in the art that siRNAs can be produced byprocessing hairpin RNAs in the cell. Hairpin RNAs can be synthesizedexogenously or can be formed by transcribing from RNA polymerase IIIpromoters in vivo. Examples of making and using hairpin RNAs for genesilencing in mammalian cells are described in, for example, Paddison etal., Genes Dev, 2002, 16: 948-58; McCaffrey et al., Nature, 2002, 418:38-9; McManus et al., RNA, 2002, 8: 842-50; Yu et al., Proc. Natl. Acad.Sci. USA, 2002, 99: 6047-52). Preferably, such hairpin RNAs areengineered in cells or in an animal to ensure continuous and stablesuppression of a desired gene.

PCT application WO 01/77350 describes an exemplary vector forbi-directional transcription of a transgene to yield both sense andantisense RNA transcripts of the same transgene in a eukaryotic cell.Accordingly, in certain embodiments, the present invention provides arecombinant vector having the following unique characteristics: itcomprises a viral replicon having two overlapping transcription unitsarranged in an opposing orientation and flanking a transgene for an RNAiconstruct of interest, wherein the two overlapping transcription unitsyield both sense and antisense RNA transcripts from the same transgenefragment in a host cell.

In another embodiment, the present disclosure relates to the use ofribozyme molecules designed to catalytically cleave an mRNA transcriptto prevent translation of the mRNA (see, e.g., PCT InternationalPublication WO90/11364, published Oct. 4, 1990; Sarver et al., 1990,Science 247: 1222-1225; and U.S. Pat. No. 5,093,246). While any ribozymethat cleaves the target mRNA at a site-specific recognition sequence canbe used to destroy that particular mRNA, the use of hammerhead ribozymesis preferred. Hammerhead ribozymes cleave mRNAs at locations dictated byflanking regions that form complementary base pairs with the targetmRNA. The sole requirement is that the target mRNA have the followingsequence of two bases: 5′-UG-3′. The construction and production ofhammerhead ribozymes is well known in the art and is described morefully in Haseloff and Gerlach, 1988, Nature, 334: 585-591. The ribozymesof the present invention also include RNA endoribonucleases (“Cech-typeribozymes”) such as the one which occurs naturally in Tetrahymenathermophila (known as the IVS or L-19 IVS RNA) and which has beenextensively described (see, e.g., Zaug, et al., 1984, Science, 224:574-578; Zaug and Cech, 1986, Science, 231: 470-475; Zaug, et al., 1986,Nature, 324: 429-433; published International patent application No.WO88/04300 by University Patents Inc.; Been and Cech, 1986, Cell, 47:207-216).

In a further embodiment, the invention relates to the use of DNA enzymesto inhibit expression of a targeted gene. DNA enzymes incorporate someof the mechanistic features of both antisense and ribozyme technologies.DNA enzymes are designed so that they recognize a particular targetnucleic acid sequence, much like an antisense oligonucleotide; however,much like a ribozyme, they are catalytic and specifically cleave thetarget nucleic acid. Briefly, to design an ideal DNA enzyme thatspecifically recognizes and cleaves a target nucleic acid, one of skillin the art must first identify a unique (or nearly unique) targetsequence. Preferably, the sequence is a G/C rich stretch ofapproximately 18 to 22 nucleotides. High G/C content helps insure astronger interaction between the DNA enzyme and the target sequence.When synthesizing the DNA enzyme, the specific antisense recognitionsequence that will target the enzyme to the message is divided so thatit comprises the two arms of the DNA enzyme, and the DNA enzyme loop isplaced between the two specific arms. Methods of making andadministering DNA enzymes can be found, for example, in U.S. Pat. No.6,110,462.

The methods described herein may be used to deliver a variety ofmolecules, including but not limited to small molecules (including smallmolecules that do not have optimal cell-permeability), lipids,nucleosides, nucleotides, nucleic acids, polynucleotides,oligonucleotides, antibodies, toxins, negatively charged polymers andother polymers, for example proteins, peptides, hormones, carbohydrates,or polyamines, across cellular membranes. Non-limiting examples ofpolynucleotides that can be delivered across cellular membranes usingthe compounds and methods of the invention include short interferingnucleic acid (siNA), antisense, enzymatic nucleic acid molecules,2′,5′-oligoadenylate, triplex forming oligonucleotides, aptamers, anddecoys. Biologically active molecules that may be delivered includeantibodies (e.g., monoclonal, chimeric, humanized etc.), cholesterol,hormones, antivirals, peptides, proteins, chemotherapeutics, smallmolecules, vitamins, co-factors, nucleosides, nucleotides,oligonucleotides, enzymatic nucleic acids, antisense nucleic acids,triplex forming oligonucleotides, 2,5-A chimeras, allozymes, aptamers,decoys and analogs thereof, and small nucleic acid molecules, such asshort interfering nucleic acid (siNA), short interfering RNA (siRNA),double-stranded RNA (dsRNA), micro-RNA (miRNA), antagomirs, and shorthairpin RNA (shRNA) molecules, to relevant cells and/or tissues, such asin a subject or organism.

The compounds, compositions, and methods of the invention can increasedelivery or availability of biologically active molecules (e.g., siNAs,siRNAs, miRNAs, siRNA and miRNA inhibitors, nucleic acids,polynucleotides, oligonucleotides, peptides, polypeptides, proteins,hormones, antibodies, and small molecules) to cells or tissues comparedto delivery of the molecules in the absence of the compounds,compositions, and methods of the invention. As such, the level of abiologically active molecule inside a cell, tissue, or organism isincreased in the presence of the compounds and compositions of theinvention compared to when the compounds and compositions of theinvention are absent.

The term “ligand” refers to any compound or molecule, such as a drug,peptide, hormone, or neurotransmitter that is capable of interactingwith another compound, such as a receptor, either directly orindirectly. The receptor that interacts with a ligand can be present onthe surface of a cell or can alternately be an intercellular receptor.Interaction of the ligand with the receptor can result in a biochemicalreaction, or can simply be a physical interaction or association.Non-limiting examples of ligands include sugars and carbohydrates suchas galactose, galactosamine, and N-acetyl galactosamine; hormones suchas estrogen, testosterone, progesterone, glucocortisone, adrenaline,insulin, glucagon, cortisol, vitamin D, thyroid hormone, retinoic acid,and growth hormones; growth factors such as VEGF, EGF, NGF, and PDGF;cholesterol; bile acids; neurotransmitters such as GABA, Glutamate,acetylcholine; NOGO; inostitol triphosphate; diacylglycerol;epinephrine; norepinephrine; Nitric Oxide, peptides, vitamins such asfolate and pyridoxine, drugs, antibodies and any other molecule that caninteract with a receptor in vivo or in vitro. The ligand can be attachedto a compound of the invention using a linker molecule, such as anamide, amido, carbonyl, ester, peptide, disulphide, silane, nucleoside,abasic nucleoside, polyether, polyamine, polyamide, peptide,carbohydrate, lipid, polyhydrocarbon, phosphate ester, phosphoramidate,thiophosphate, alkylphosphate, or photolabile linker. In one embodiment,the linker is a biodegradable linker.

Linkers.

A variety of linkers may be used to link the substrate capable of beingtransported to the active agent. For example, degradable and cleavablelinkers may be used.

The term “degradable linker” as used herein, refers to linker moietiesthat are capable of cleavage under various conditions. Conditionssuitable for cleavage can include but are not limited to pH, UVirradiation, enzymatic activity, temperature, hydrolysis, elimination,and substitution reactions, and thermodynamic properties of the linkage.The term “photolabile linker” as used herein, refers to linker moietiesas are known in the art that are selectively cleaved under particular UVwavelengths. Compounds of the invention containing photolabile linkerscan be used to deliver compounds to a target cell or tissue of interest,and can be subsequently released in the presence of a UV source.

The term “linker” as used herein is any bond, small molecule, or othervehicle which allows the substrate and the active agent to be targetedto the same area, tissue, or cell. In certain embodiments, the linker iscleavable.

In one embodiment the linker is a chemical bond between one or moresubstrates and one or more therapeutic moieties. Thus, the bond may becovalent or ionic. An example of a therapeutic complex where the linkeris a chemical bond would be a fusion protein. In one embodiment, thechemical bond is acid sensitive and the pH sensitive bond is cleavedupon going from the blood stream (pH 7.5) to the transcytotic vesicle orthe interior of the cell (pH about 6.0). Alternatively, the bond may notbe acid sensitive, but may be cleavable by a specific enzyme or chemicalwhich is subsequently added or naturally found in the microenvironmentof the targeted site. Alternatively, the bond may be a bond that iscleaved under reducing conditions, for example a disulfide bond.

Alternatively, the bond may not be cleavable.

Any kind of acid cleavable or acid sensitive linker may be used.Examples of acid cleavable bonds include, but are not limited to: aclass of organic acids known as cipolycarboxylic alkenes. This class ofmolecule contains at least three carboxylic acid groups (COOH) attachedto a carbon chain that contains at least one double bond. Thesemolecules as well as how they are made and used is disclosed in Shen, etal. U.S. Pat. No. 4,631,190.

Alternatively, molecules such asamino-sulfhydryl cross-linking reagentswhich are cleavable under mildly acidic conditions may be used. Thesemolecules are disclosed in Blattler et al., U.S. Pat. No. 4,569,789.

Alternatively, the acid cleavable linker may be a time-release bond,such as a biodegradable, hydrolyzable bond. Typical biodegradablecarrier bonds include esters, amides or urethane bonds, so that typicalcarriers are polyesters, polyamides, polyurethanes and othercondensation polymers having a molecular weight between about 5,000 and1,000,000. Examples of these carriers/bonds are shown in Peterson, etal., U.S. Pat. No. 4,356,166. Other acid cleavable linkers may be foundin U.S. Pat. Nos. 4,569,789 and 4,631,190 or Blattner et al. inBiochemistry 24: 1517-1524 (1984). The linkers are cleaved by naturalacidic conditions, or alternatively, acid conditions can be induced at atarget site as explained in Abrams et al., U.S. Pat. No. 4,171,563.

Examples of linking reagents which contain cleavable disulfide bonds(reducable bonds) include, but are not limited to “DPDPB”,1,4-di-[3′-(2′-pyridyldithio) propionamido] butane; “SADP”,(N-succinimidyl (4-azidophenyl) 1,3′-dithiopropionate); “Sulfo-SADP”(Sulfosuccinimidyl (4-azidophenyldithio) propionate; “DSP”-Dithio bis(succinimidylproprionate); “DTSSP”-3,3′-Dithiobis(sulfosuccinimidylpropionate); “DTBP”-dimethyl3,3dithiobispropionimidate-2HCI, all available from Pierce Chemicals(Rockford, Ill.).

Examples of linking reagents cleavable by oxidation are“DST”-disuccinimidyl tartarate; and “Sulfo-DST”-disuccinimidyltartarate. Again, these linkers are available from PierceChemicals.

Examples of non-cleavable linkers are “Sulfo-LC-SMPT”-(sulfosuccinimidyl6-[alphamethyl-alpha-(2-pyridylthio)toluamido}hexanoate; “SMPT”;“ABH”-Azidobenzoyl hydrazide;“NHS-ASA”-N-Hydroxysuccinimidyl-4-azidosalicyclic acid;“SASD”-Sulfosuccinimidyl 2-(pazidosalicylamido)ethyl-1,3-dithiopropionate; “APDP”-N-{4-(p-azidosalicylamido) buthy}-3′(2′-pyidyldithio) propionamide; “BASED”-Bis-[beta-(4-azidosalicylamido)ethyl] disulfide; “HSAB”-N-hydroxysuccinimidyl-4 azidobenzoate;“APG”-p-Azidophenyl glyoxal monohydrate; “SANPAH”-N-Succiminidyl-6(4′-azido-2′-mitrophenyl-amimo) hexanoate;“Sulfo-SANPAH”-Sulfosuccinimidyl6-(4′-azido-2′-nitrophenylamino)hexanoate; “ANB-NOS” N-5-Azido-2-nitrobenzyoyloxysuccinimide;“SAND”-Sulfosuccinimidyl-2-(m-azido-o-mitrobenzamido)-ethyl-1,3′-dithiopropionate;“PNP-DTP”-p-nitrophenyl-2-diazo-3,3,3-trifluoropropionate;“SMCC”-Succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate;“Sulfo-SMCC”-Sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate;“MBS” m-Maleimidobenzoyl-N-hydroxysuccinimide ester;“sulfo-MBS”-m-Maleimidobenzoyl-N-hydroxysulfosuccinimide ester;“SIAB”-N-Succinimidyl (4-iodoacetyl)aminobenzoate;“SulfSIAB”-N-Sulfosuccinimidyl (4-iodoacetyl)aminobenzoate;“SMPB”-Succinimidyl 4-(pmalenimidophenyl) butyrate;“Sulfo-SMPB”-Sulfosuccinimidyl 4-(p-malenimidophenyl) butyrate;“DSS”-Disuccinimidyl suberate; “BSSS”-bis(sulfosuccinimidyl) suberate;“BMH”-Bis maleimidohexane; “DFDNB”-1,5-difluoro-2,4-dinitrobenzene;“DMA”-dimethyl adipimidate 2HCI; “DMP”-Dimethyl pimelimidate-2HCI;“DMS”-dimethyl suberimidate-2-HCl; “SPDPN-succinimidyl-3-(2-pyridylthio)propionate; “Sulfo-HSAB”-Sulfosuccinimidyl 4-(pazidophenyl) butyrate;“Sulfo-SAPB”-Sulfosuccinimidyl 4-(p-azidophenylbutyrate);“ASIB”-1-9p-azidosalicylamido)-4-(iodoacetamido) butane;“ASBA”-4-(p-Azidosalicylamido) butylamine. All of these linkers areavailable from Pierce Chemicals.

In another embodiment the linker is a small molecule such as a peptidelinker. In one embodiment the peptide linker is not cleavable. In afurther embodiment the peptide linker is cleavable by base, underreducing conditions, or by a specific enzyme. In one embodiment, theenzyme is indigenous. Alternatively, the small peptide may be cleavableby an non-indigenous enzyme which is administered after or in additionto the therapeutic complex. Alternatively, the small peptide may becleaved under reducing conditions, for example, when the peptidecontains a disulfide bond. Alternatively, the small peptide may be pHsensitive. Examples of peptide linkers include: poly(L-Gly), (PolyL-Glycine linkers); poly(L-Glu), (PolyL-Glutamine linkers); poly(L-Lys), (Poly L-Lysine linkers). In one embodiment, the peptide linkerhas the formula (amino acid) n, where n is an integer between 2 and 100,preferably wherein the peptide comprises a polymer of one or more aminoacids.

In a further embodiment, the peptide linker is cleavable by proteinasesuch as one having the sequenceGly-(D)Phe-Pro-Arg-Gly-Phe-Pro-Ala-Gly-Gly (SEQ ID NO:13) (Suzuki, et al. 1998,J. Biomed. Mater. Res. October; 42 (1): 112-6). This embodiment has beenshown to be advantageous for the treatment of bacterial infections,particularly Pseudomonas aeruginosa. Gentamicin or an alternateantibiotic is cleaved only when the wounds are infected by Pseudomonasaeruginosa because there is significantly higher activity ofthrombin-like proteinase enzymes then in noninfected tissue.

In a further embodiment the linker is a cleavable linker including, poly(ethylene glycol) (PEG) and a dipeptide,L-alanyl-L-valine (Ala-Val),cleavable by the enzyme thermolysin. This linker is advantageous becausethermolysin-like enzyme has been reported to be expressed at the site ofmany tumors. Alternatively, a 12 residue spacerThr-Arg-His-Arg-Gln-Pro-Arg-Gly-Trp-Glu-Gln-Leu (SEQ ID NO: 14) may beused which contains the recognition site for the protease furin (Goyal,et al. Biochem. J. 2000 Jan. 15; 345 Pt 2: 247-254).

The chemical and peptide linkers can be bonded between the substrate andthe active agent by techniques known in the art for conjugate synthesis,i.e. using genetic engineering, or chemically. The conjugate synthesiscan be accomplished chemically via the appropriate antibody by classicalcoupling reactions of proteins to other moieties at appropriatefunctional groups.

Examples of the functional groups present in proteins and utilizednormally for chemical coupling reactions are outlined as follows. Thecarbohydrate structures may be oxidized to aldehyde groups that in turnare reacted with a compound containing the groupH2NNH—R (wherein R isthe compound) to the formation of aC═NH—NH—R group. The thiol group(cysteines in proteins) may be reacted with a compound containing athiol-reactive group to the formation of a thioether group or disulfidegroup. The free amino group (at the amino terminus of a protein or on alysine) in amino acid residues may be reacted with a compound containingan electrophilic group, such as an activated carboxy group, to theformation of an amide group. Free carboxy groups in amino acid residuesmay be transformed to a reactive carboxy group and then reacted with acompound containing an amino group to the formation of an amide group.

The linker may alternatively be a liposome. Many methods for thepreparation of liposomes are well known in the art. For example, thereverse phase evaporation method, freezethaw methods, extrusion methods,and dehydration-rehydration methods. (see Storm, et al. PSTT 1:19-31(1998),).

The liposomes may be produced in a solution containing the active agentso that the substance is encapsulated during polymerization.Alternatively, the liposomes can be polymerized first, and thebiologically active substance can be added later by resuspending thepolymerized liposomes in a solution of a biologically active substanceand treating with sonication to affect encapsulation of the activeagent. The liposomes can be polymerized in the presence of the substratesuch that the substrate becomes a part of the phospholipid bilayer. Inone embodiment, the liposome contains the active agent on the inside andthe substrate on the outside.

The liposomes contemplated in the present invention can comprise avariety of structures. For example, the liposomes can be multilamellarlarge vesicles (MLV), oligolamellar vesicles (OLV), unilamellar vesicles(UV), small unilamellar vesicles (SUV), medium sized unilamellarvesicles(MUV), large unilamellar vesicles (LUV), giant unilamellarvesicles (GUV), or multivesicular vesicles (MVV). Each of these liposomestructures are well known in the art (see Storm, et al. PSTT 1: 19-31(1998)).

In one embodiment, the liposome is a “micromachine” that evulsespharmaceuticals for example by the application of specific frequencyradio waves. In another embodiment, the liposomes can be degraded suchthat they will release the active agent in the targeted cell, forexample, the liposomes may be acid or alkaline. sensitive, or degradedin the presence of a low or high pH, such that the active agent isreleased within the cell. Alternatively, the liposomes may be unchargedso that they will be taken up by the targeted cell. The liposomes mayalso be pH sensitive or sensitive to reducing conditions.

One type of liposome which may be advantageously used in the presentinvention is that identified in Langer et al., U.S. Pat. No. 6,004,534,issued Dec. 21, 1999. In this application a method of producing modifiedliposomes which are prepared by polymerization of double and triplebond-containing monomeric phospholipids is disclosed. These liposomeshave surprisingly enhanced stability against the harsh environment ofthe gastrointestinal tract. Thus, they have utility for oral and/ormucosal delivery of the active agent. It has also been shown that theliposomes may be absorbed into the systemic circulation and lymphaticcirculation. The liposomes are generally prepared by polymerization(i.e., radical initiation or radiation) of double and triplebond-containing monomeric phospholipids.

In other embodiments of the present invention, the linker can also be aliposome having a long blood circulation time. Such liposomes are wellknown in the art, (see U.S. Pat. Nos., 5,013,556; 5,225,212; 5,213,804;5,356,633; and 5,843,473). Liposomes having long blood circulation timeare characterized by having a portion of their phosphoslipidsderivatized with polyethylene glycol (PEG) or other similar polymer. Insome embodiments, the end of the PEG molecule distal to the phospholipidmay be activated so a to be chemically reactive. Such a reactive PEGmolecule can be used to link a substrate to the liposome. One example ofa reactive PEG molecule is the maleimide derivative of PEG described inU.S. Pat. No. 5,527,528).

Alternatively, the linker may be a microcapsule, a nanoparticle, amagnetic particle, and the like (Kumar, J. Pharm. Sci., May-August 3 (2)234-258, 2000; and Gill et al., Trends Biotechnol. November; 18(11):469-79, 2000), with the lipophilic active agent on or in the container,and the container functioning as the linker in the therapeutic complex.

Alternatively, the linker may be a photocleavable linker. For example, a1-2-(nitrophenyl)ethyl moiety can be cleaved using 300 to 360 nm light(see Pierce catalog no. 21332ZZ). It can be envisioned that thephotocleavable linker would allow activation and action of the drug inan even more specific area, for example a particular part of the organ.The light could be localized using a catheter into the vessel.Alternatively, light may be used to localize treatment to a specificpart of the digestive tract and the light may be manipulated through anatural orifice to the area.

Alternatively, the light can be surgically manipulated to the area.

Alternatively, the linker may not be cleavable, but the active agent orsubstrate is. An example of this is when the active agent is a prodrugand the enzyme which cleaves the prodrug is administered with thetherapeutic complex. Alternatively, the enzyme is part of thetherapeutic complex or indigenous and the prodrug is administeredseparately. Preferably, the enzyme or prodrug which is administeredseparately is administered within about 48 hours of the firstadministration. Alternatively, the prodrug or enzyme which isadministered separately may be administered between about 1 min and 24hours, alternatively between about 2 min and 8 hours.

The prodrug or enzyme which is administered separately, may bereadministered at a later date and may continue to be administered untilthe effect of the drug is not longer needed.

According to yet another embodiment of the invention, there are providedmethods for treating a disease or disorder in a cell or tissueexpressing a nucleoside transport pathway. The method includesadministering to a patient having the disease or disorder a conjugateincluding a substrate that is capable of being transported by thenucleoside transport pathway expressed in the affected cell or tissueand an active agent for treating disease or disorder, wherein theconjugate is also transported by the nucleoside transport pathway. Inthis way, the conjugate is transported into the affected cells ortissue, thereby delivering the active agent.

Diseases or disorders which may be treated using a conjugate of theinvention include diseases or disorders involving tissues such as muscle(including skeletal muscle and cardiac muscle), glycogen-storing cells,vascular endothelium, heart, brain, placenta, thymus, pancreas,prostate, kidney, blood, skin, and ENT2-expressing cancer cells.

In certain embodiments the disease or disorder involves muscle such asskeletal or cardiac muscle and the conjugate is transported into themuscle cells (such as skeletal muscle cells or cardiac muscle cells),thereby delivering the active agent. In certain embodiments, the muscledisorder is selected from the group consisting of cachexia, muscledystrophies, lysosomal muscle disorders, skeletal muscle disorders,smooth muscle disorders, and cardiac muscle disorders. In certainembodiments, these designations may overlap. Muscle dystrophies includeBecker's muscular dystrophy (BMD), Congenital muscular dystrophy,Duchenne muscular dystrophy (DMD), Distal muscular dystrophy,Emery-Dreifuss muscular dystrophy, Facioscapulohumeral musculardystrophy (FSHD), Limb-girdle muscular dystrophy (LGMD), Myotonicmuscular dystrophy, and Oculopharyngeal muscular dystrophy. In certainembodiments, a lysosomal disorder is Pompe Disease, Hurler Syndrome,Fabry Disease, Maroteaux-Lamy Syndrome, Morquio Syndrome, HunterSyndrome, Farber Disease, Krabbe Disease, Sly Syndrome, Sanfilippo(including A, B, and D), Morquio A, Multiple Sulfatase Deficiency,Metachromatic Leukodystrophy, Mucolipidosis IV, G.sub.MI Gangliosidosis,Galactosialidosis, Tay-Sachs and Tay-Sachs Variants, Sandhoff,Fucsidosis, Schindler Disease, Sialidosis, Aspartylglucosaminuria,Wolman Disease, Farber Lipogranulomatosis, and Nieman-Pick disease. Incertain embodiments, the cardiac muscle disorder is cardiomyopathy,cardiac ischemia, congestive heart failure, ischemia-reperfusion injury,Coronary heart disease, Cardiovascular disease, Ischaemic heart disease,Heart failure, Hypertensive heart disease, Inflammatory heart disease,and Valvular heart disease. The muscle disorder may be sarcopenia. Insome embodiments, the muscle disorder is muscle wasting caused byanother disease, such as AIDS or cancer. Other muscle disorders includediseases of the neuromuscular junction, such as myasthenia gravis,Lambert-Eaton syndrome, and Congenital Myasthenic Syndrome, motor neurondiseases (such as ALS, spinal muscular atrophy, Charcot-Maria-Toothdisease, and Freidrich's Ataxia), inflammatory myopathies (such asdermatomyositis, polymyositis, and inclusion body myositis), endocrineabnormalities (such as hyperthyroid myopathy), myotonia, nemalinemyopathy, and myotubular myopathy. Enzyme deficiency disorders of themuscles include Phosphorylase Deficiency, Acid Maltase Deficiency,Mitochondrial Myopathy, Carnitine Palmityl Transferase Deficiency,Phosphoglycerate Kinase Deficiency, and Phosphoglycerate MutaseDeficiency.

In particular embodiments, the active agent effective in the treatmentof a skeletal muscle disorder may be, for example, an enzyme that islacking in a patient with the muscle disorder. For example, thefollowing skeletal muscle diseases and disorders may be treated with thefollowing enzymes, or a nucleic acid that modulates the expression ofsaid enzymes, in accordance with the methods herein: α-glucosidase(Pompe Disease), α-L-iduronidase (Hurler Syndrome), α-galactosidase A(Fabry Disease), arylsulfatase (Maroteaux-Lamy Syndrome),N-acetylgalactosamine-6-sulfatase or β-galactosidase (Morquio Syndrome),iduronate 2-sulfatase (Hunter Syndrome), ceramidase (Farber Disease),galactocerebrosidase (Krabbe Disease), β-glucuronidase (Sly Syndrome),Heparan N-sulfatase (Sanfilippo A), N-Acetyl-α-glucosaminidase(Sanfilippo B), Acetyl CoA-α-glucosaminide N-acetyl transferase,N-acetyl-glucosamine-6 sulfatase (Sanfilippo D), Galactose 6-sulfatase(Morquio A), Arylsulfatase A, B, and C (Multiple Sulfatase Deficiency),Arylsulfatase A Cerebroside (Metachromatic Leukodystrophy), Ganglioside(Mucolipidosis IV), Acid β-galactosidase G.sub.MI Gaiglioside (G.sub.MIGangliosidosis), Acid β-galactosidase (Galactosialidosis),Hexosaminidase A (Tay-Sachs and Variants), Hexosaminidase B (Sandhoff),α-fucosidase (Fucsidosis), α-N-Acetyl galactosaminidase (SchindlerDisease), Glycoprotein Neuraminidase (Sialidosis), Aspartylglucosamineamidase (Aspartylglucosaminuria), Acid Lipase (Wolman Disease), AcidCeramidase (Farber Lipogranulomatosis), Lysosomal Sphingomyelinase andother Sphingomyelinase (Nieman-Pick). In certain embodiments, the activeagent is dystrophin, components of dystrophin-glycoprotein complex, thelaminin-α2 chain, fukutin-related protein, LARGE, fukutin, EMD, LMNA,DMPK, ZNF9, and PABPN1, or a nucleic acid that modulates the expressionof said proteins.

In certain embodiments the disease or disorder involves glycogen-storingcells and the conjugate is transported into the glycogen-storing cells,thereby delivering the active agent. Glycogen-storing cells includemuscle cells, liver cells, and also kidney and intestinal cells. Incertain embodiments, the glycogen-storage disorder is selected from thegroup consisting of Glycogen synthase deficiency, Glucose-6-phosphatasedeficiency (von Gierke disease), Debranching enzyme deficiency(Forbes-Cori disease), Transglucosidase deficiency, (Andersen disease,amylopectinosis), Myophosphorylase deficiency (McArdle disease),Phosphorylase deficiency (Hers disease), and Phosphofructokinasedeficiency (Tauri disease). In particular embodiments, the active agenteffective in the treatment of a glycogen-storage disorder is Glycogensynthase, Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase, or a nucleic acid that up-regulates theexpression of the deficient proteins.

In certain embodiments the disease or disorder involves vascularendothelium and the conjugate is transported into the vascularendothelium, thereby delivering the active agent. In certainembodiments, the vascular endothelium disorder is selected from thegroup consisting of inappropriate angiogenesis (for example, surroundinga tumor), deficient angiogenesis (for example, in a slowly-healing woundor ulcer), restenosis, atherosclerosis, scarring after surgery orinjury, and vasculitis. Examples of diseases associated withuncontrolled angiogenesis that may be treated with the compositions andmethods herein include, but are not limited to retinal/choroidalneovascularization and corneal neovascularization. Examples ofretinal/choroidal neovascularization include, but are not limited to,Bests diseases, myopia, optic pits, Stargarts diseases, Pagets disease,vein occlusion, artery occlusion, sickle cell anemia, sarcoid, syphilis,pseudoxanthoma elasticum carotid apo structive diseases, chronicuveitis/vitritis, mycobacterial infections, Lyme's disease, systemiclupus erythematosus, retinopathy of prematurity, Eales disease, diabeticretinopathy, macular degeneration, Bechets diseases, infections causinga retinitis or chroiditis, presumed ocular histoplasmosis, parsplanitis, chronic retinal detachment, hyperviscosity syndromes,toxoplasmosis, trauma and post-laser complications, diseases associatedwith rubesis (neovascularization of the angle) and diseases caused bythe abnormal proliferation of fibrovascular or fibrous tissue includingall forms of proliferative vitreoretinopathy. Examples of cornealneovascularization include, but are not limited to, epidemickeratoconjunctivitis, Vitamin A deficiency, contact lens overwear,atopic keratitis, superior limbic keratitis, pterygium keratitis sicca,sjogrens, acne rosacea, phylectenulosis, diabetic retinopathy,retinopathy of prematurity, corneal graft rejection, Mooren ulcer,Terrien's marginal degeneration, marginal keratolysis, polyarteritis,Wegener sarcoidosis, Scleritis, periphigoid radial keratotomy,neovascular glaucoma and retrolental fibroplasia, syphilis, Mycobacteriainfections, lipid degeneration, chemical burns, bacterial ulcers, fungalulcers, Herpes simplex infections, Herpes zoster infections, protozoaninfections and Kaposi sarcoma. Example of deficient angiogenesis includeulcers such as skin ulcers and diabetic ulcers. In one embodiment, theactive agent effective in the treatment of a disease of the vascularendothelium is serum amyloid P (SAP), or a nucleic acid that increasesSAP expression. SAP inhibits fibrocytes from causing pathologicalscarring lesions. In another embodiment, the disease of the vascularendothelium is atherosclerosis, which may be treated using statins,niacin, intestinal cholesterol absorption-inhibiting supplements such asezetimibe and fibrates, aspirin, human Apo-A1 Milano HDL, or a nucleicacid that increases Apo-A1 Milano HDL expression. One may alsoadminister nucleic acids that reduce synthesis of cholesterol, such assiRNA constructs designed to reduce expression of cholesterol syntheticenzymes. Cholesterol synthetic enzymes include HMG-CoA synthase, HMG-CoAreductase, mevalonate kinase, phosphomevalonate kinase, and lanosterolsynthase.

In certain embodiments the disease or disorder involves the brain andthe conjugate is transported into the brain cells, thereby deliveringthe active agent. In certain embodiments, the brain disorder is selectedfrom the group consisting of neurodegenerative diseases (such asAlzheimer's disease, Parkinson's disease, motor neuron disease, andHuntington's disease), mental illnesses, such as clinical depression,schizophrenia, bipolar disorder, and post-traumatic stress disorder;infectious diseases including meningitis, viral, bacterial, and priondiseases, inherited disorders such as Tay-Sachs disease, Fragile Xsyndrome, and Down syndrome, and lysosomal storage disorders. Inparticular embodiments, the active agent effective in the treatment of adisease of the brain is an enzyme absent (or present at reduced levels)in a patient with a lysosomal storage disorder; examples of lysosomaldisorders, and compositions for treating them, are listed above.

In certain embodiments the disease or disorder involves the placenta andthe conjugate is transported into the placental cells, therebydelivering the active agent. In certain embodiments, the placentaldisorder is selected from the group consisting of Placenta accreta,Placenta praevia, and Placental abruption.

In certain embodiments the disease or disorder involves the thymus andthe conjugate is transported into cells of the thymus, therebydelivering the active agent. In certain embodiments, the thymus disorderis selected from the group consisting of an autoimmune disease, adisease resulting from faulty positive selection or faulty negativeselection of T cells, and cancer of the thymus. Some examples ofautoimmune diseases include Alopecia Areata, Ankylosing Spondylitis,Antiphospholipid Syndrome, Autoimmune Addison's Disease, AutoimmuneHemolytic Anemia, Autoimmune Hepatitis, Behcet's Disease, BullousPemphigoid, Cardiomyopathy, Celiac Sprue-Dermatitis, Chronic FatigueImmune Dysfunction Syndrome (CFIDS), Chronic Inflammatory DemyclinatingPolyneuropathy, Churg-Strauss Syndrome, Cicatricial Pemphigoid, CRESTSyndrome, Cold Agglutinin Disease, Crohn's Disease, Discoid Lupus,Essential Mixed Cryoglobulinemia, Fibromyalgia-Fibromyositis, Graves'Disease, Guillain-Barr, Hashimoto's Thyroiditis, Hypothyroidism,Idiopathic Pulmonary Fibrosis, Idiopathic Thrombocytopenia Purpura(ITP), IgA Nephropathy, Insulin dependent Diabetes, Juvenile Arthritis,Lichen Planus, Lupus, Meniere's Disease, Mixed Connective TissueDisease, Multiple Sclerosis, Myasthenia Gravis, Pemphigus Vulgaris,Pernicious Anemia, Polyarteritis Nodosa, Polychondritis, PolyglandularSyndromes, Polymyalgia Rheumatica, Polymyositis and Dermatomyositis,Primary Agammaglobulinemia, Primary Biliary Cirrhosis, Psoriasis,Raynaud's Phenomenon, Reiter's Syndrome, Rheumatic Fever, RheumatoidArthritis, Sarcoidosis, Scleroderma, Sjogren's Syndrome, Stiff-ManSyndrome, Takayasu Arteritis, Temporal Arteritis/Giant Cell Arteritis,Ulcerative Colitis, Uveitis, Vasculitis, Vitiligo, Wegener'sGranulomatosis, and myasthenia gravis. In particular embodiments, theactive agent effective in the treatment of a disease of the thymus isimmunosuppressive or anti-inflammatory. The agent may be, for example,an antibody including muromab, basiliximab, and daclizumab, or a nucleicacid encoding one of those antibodies. Examples of immunosuppressive andanti-inflammatory drugs that may be used as the active agent includecorticosteroids, rolipram, calphostin, CSAIDs; interleukin-10,glucocorticoids, salicylates, nitric oxide; nuclear translocationinhibitors, such as deoxyspergualin (DSG); non-steroidalantiinflammatory drugs (NSAIDs) such as ibuprofen, celecoxib androfecoxib; steroids such as prednisone or dexamethasone; antiviralagents such as abacavir; antiproliferative agents such as methotrexate,leflunomide, FK506 (tacrolimus, Prograf); cytotoxic drugs such asazathioprine and cyclophosphamide; TNF-.alpha. inhibitors such astenidap, anti-TNF antibodies or soluble TNF receptor, and rapamycin(sirolimus or Rapamune) or derivatives thereof. When the disease iscancer of the thymus, the active agent may be a chemotherapeutic drug orother type of anti-cancer therapeutic.

In certain embodiments the disease or disorder involves the pancreas andthe conjugate is transported into cells of the pancreas, therebydelivering the active agent. In certain embodiments, the pancreasdisorder is selected from the group consisting of Pancreatitis, Diabetesmellitus, Exocrine pancreatic insufficiency, complications of Cysticfibrosis, Pseudocysts, or pancreatic cancer. In particular embodiments,the active agent effective in the treatment of a disease of the pancreasis insulin, a Pancreatic Enzyme Product (PEP) such as pancrelipase, or anucleic acid that up-regulates expression of the same.

In certain embodiments the disease or disorder involves the prostate andthe conjugate is transported into cells of the prostate, therebydelivering the active agent. In certain embodiments, the prostatedisorder is selected from the group consisting of Prostatitis, Benignprostatic hyperplasia, or Prostate cancer. In particular embodiments,the active agent effective in the treatment of a disease of the prostateis an anti-cancer agent; examples of such agents are listed elsewhere inthis application.

In certain embodiments the disease or disorder involves the kidney andthe conjugate is transported into cells of the kidney, therebydelivering the active agent. In certain embodiments, the kidney disorderis selected from the group consisting of Diabetic nephropathy,Glomerulonephritis, Hydronephrosis, Kidney stones, Kidney tumors (suchas Wilms tumor and Renal cell carcinoma), Lupus nephritis, Minimalchange disease, Pyelonephritis, nephrotic syndrome, and Renal failure(such as Acute renal failure and Stage 5 Chronic Kidney Disease). Inparticular embodiments, the active agent effective in the treatment of adisease of the kidney is an agent that treats autoimmune disease, or ananti-cancer therapeutic, both of which are listed elsewhere in thepresent application.

In certain embodiments the disease or disorder involves the blood andthe conjugate is transported into cells of the blood, thereby deliveringthe active agent. In certain embodiments, the blood disorder is selectedfrom the group consisting of: primary immunodeficiency (including SCID,hemophilia A, and hemophilia B), reduced hematopoietic function, reducedimmune function, reduced neutrophil count, reduced neutrophilmobilization, mobilization of peripheral blood progenitor cells, sepsis,severe chronic neutropenia, bone marrow transplants, infectiousdiseases, leucopenia, thrombocytopenia, anemia, bone marrow disorderscaused by radiation, chemical or chemotherapeutic induced bone marrowaplasia or myelosuppression, acquired immune deficiency syndrome, andpolycythemia rubra vera. In particular embodiments, the active agenteffective in the treatment of a disease of the blood is selected fromthe group consisting of corticosteroids, anti-leukemic agents, growthfactors, and clotting factors. In certain embodiments, the clottingfactor is Factor VIII or IX. In certain aspects, SCID is caused by arecessive mutation and may be treated by administering a wild-type copyof the missing protein (or a nucleic acid encoding that protein). Forexample, X-linked SCID may be treated with IL2RG, Jak3 gene mutationsmay be treated with JAK3, ADA gene mutations may be treated with ADA,IL-7R alpha-chain mutations may be treated with IL7R alpha, CD3 delta orepsilon mutations may be treated with CD3 delta or epsilon, RAG1/RAG2mutations may be treated with RAG1/RAG2, Artemis gene mutations may betreated with ARTEMIS, and CD45 gene mutations may be treated with CD45.Other types of primary immunodeficiency are deficiencies in thefollowing proteins: DNA ligase type I, CD40 ligand, CD40, Purinenucleoside phosphorylase (PNP), MHC class II, CD3γ, CD8, ZAP-70, TAP-½,Winged helix protein, CD19, TACI, BAFF receptor, AICDA, uracil-DNAglycosylase, perforin, MUNC13D, syntaxin 11, CD95, Fas ligand, CASP8,and CASP10. These deficiencies may be treated by administration of thedeficient protein or a nucleic acid encoding it.

In certain embodiments the disease or disorder involves the skin and theconjugate is transported into cells of the skin, thereby delivering theactive agent. In certain embodiments, the skin disorder is selected fromthe group consisting of dermatomyositis, papulosquamous dermatoses,bacterial dermatoses, viral dermatoses, mycolic skin infections,granulomatous dermatoses, parasitic skin dermatoses, exfoliativedermatitis, bullous dermatoses, pigmented dermatoses, photosensitivedermatoses, dermatoses caused by collagen diseases, dermatoses due tointernal diseases, xerosis, urticaria, atopic dermatitis, eczyma, lichensimplex chronicus, psoriasis, scabies, wound, sun burn, cold sores,acne, insect bite, radiotherapy or chemotherapy-induced dermatitis,paraneoplastic syndrome, malignancy, melanoma, primary skin cancer, andmetastatic skin cancer. In particular embodiments, the active agenteffective in the treatment of a disease of the skin is anthralin,calpotriene, coal tar, diclofenac, T4 endonuclease, isotretinoin,acitretin, cidofoir, a corticosteroid, an antibiotic, an analgesic, animmunomodulator, including oral immunomodulator such as tacrolimus andpimecrolimus, and topical immunomodulators; an immunosuppressant, ananti-angiogenic, including anti-VEGF, anti-FGF, anti-EGF and anti-HGF; aleukotriene modifier, an aminosalicylate, an anesthetic, a non-steroidalanti-inflammatory, a modifier of a solubilized interleukin receptor, aninhibitor of a tyrosine-kinase receptor, a protein kinase C inhibitor,methotrexate, cyclosporine, and methylprednisolone acetate.

In certain embodiments the disease or disorder is a type of cancer andthe conjugate is transported into cancer cells, thereby delivering theactive agent. In certain embodiments, the type of cancer is selectedfrom the group consisting of rhabdomyosarcoma, ovarian cancer, coloncancer, and breast cancer. In other embodiments, the cancer is selectedfrom leukemia, lymphomas, melanomas, squamous cell carcinomas, breastcancer, prostrate cancer, bladder cancer, lung cancer including nonsmall-cell lung cancer and small-cell lung cancer, ovarian cancer, coloncancer, squamous cell carcinoma, astrocytoma, Kaposi's sarcoma,glioblastoma, bladder cancer, head and neck cancer, glioma, colorectalcancer, genitourinary cancer and gastrointestinal cancer. In certainembodiments, the active agent is a chemotherapeutic drug.Chemotherapeutic drugs are well-known in the art and include alkylatingagents such as cisplatin, anti-metabolites such as mercaptopurine,taxanes such as paclitaxel, topoisomerase inhibitors such as topotecan,and antitumor antibiotics such as doxorubicin. Anti-tumor active agentsalso include antibodies such as Herceptin. In particular embodiments,the active agent effective in the treatment of cancer is a protein (ornucleic acid encoding the same) selected from: a bispecific antibodythat binds Pax-FKHR fusion protein or a tumor suppressor such as p53,pRb, PTEN, APC, and CD95, BRCA1, BRCA2, DNA repair enzymes, proapoptoticgenes, p16^(INK4a), WT1, NF1 (neurofibromin 1), NF2 (merlin orneurofibromin 2), TSC1 (hamartin), TSC2 (tuberin), DPC4, SMAD4, DCC,LKB1, STK11, MSH2, MLH1, CDH1 (E-cadherin), VHL, PTCH, (patched), MENI,BLM, NBS1, MRE11A, ATM, hRad50, NER enzymes (such as XPA, XPB, XPC, XPD,DDB2, ERCC4, RAD2, and POLH), ERCC6, ERCC8, RECQL2, FANCA, FANCC,FANCD2, FANCE, FANCF, FANCG, FANCI, FANCJ, FANCL, FANCM, MLH1, MSH2,MSH6, PMS, and PMS2.

In certain embodiments the compositions and methods herein may be usedto treat a disease or disorder involving dysfunction of nuclearreceptors, and the conjugate is transported into cells in which alterednuclear receptor function is desired. In certain embodiments, thenuclear receptors are steroid, thyroid, retinoid, or orphan nuclearreceptors. In certain embodiments, the orphan nuclear receptor is a SAR(selective androgen receptor), PPAR, PPARβ, PPAR, NUC1, FAAR, PPAR,RevErbA, EAR-1, RVR, RevErbAβ, BD73, HZF2, ROR, RZR, RORβ, RZR13, ROR,TOR, LXR, RLD1, LXRβ, UR, NER, RIP15, OR1, FXR, RIP14, HRR1, PXR.1,PXR.2, SXR, ONR1, xOR6, BXR, hCAR1, MB67, mCAR1, HNF4, HNF4β, HNF4, RXR,RXRβ, H2RIIBP, RXR, TR2, TR2-11, xDOR2, aDOR1, TR4, TAK1, TR2R1, T1x,TLL, xTLL, COUP-TFI, COUPTFA, EAR3, SVP44, COUP-TFII, COUPTFB ARPI,SVP40, xCOUP-TFIII, COUP-TF, SVP46, EAR2, ERR, ERR1, ERRβ, ERR2, ERR,NGFI-B, NUR77, N10, TR3, NAKI, TISI, NURR1, NOT, RNR1, HZF-3, TINUR,TR3β, NOR-1, MINOR, TEC, CHN, FTZ-F1, SF1, ELP, AD4BP, FTF, LRH1, PHR1,CPF, FFLR, FF1rA, GCNF, RTR, DAX1, AHCH, or SHP. Depending on thedisease to be treated, one of skill in the art will recognize whetherthe disease should be treated by increasing the levels of a nuclearreceptor or decreasing the levels or activity of a nuclear receptor.Levels of the nuclear receptor may be increased, for example, byadministering a nucleic acid encoding the nuclear receptor. Activity ofthe nuclear receptor may be decreased, by example, by administering aninhibitory antibody. Nuclear receptors, and the diseases caused bymutations in them, are as follows: Androgen receptor (CAIS/PAIS,complete/partial androgen insensitivity syndrome; Gynecomastia;interfility; SBMA; Kennedy's disease; Prostate Cancer; perinealhypospadias), DAX-1 (adrenal hypoplasia congenita, Adrenalinsufficiency, delayed-onset, and hypogonadotropic hypogonadism),Vitamin 3D receptor (Vitamin D Resistant-rickets type IIA); HNF4 alpha(Maturity-onset diabetes of the young); Mineralocoricoid receptor(Pseudohypoaldosteronism, type 1; autosomal dominant; Hypertension,early-onset, autosomal dominant, with exacerbation in pregnancy),Thyroid hormone beta-1 (thyroid hormone resistance), Glucocorticoidreceptor (Primary cortisol resistance familial Glucocorticoidresistance), PPAR gamma (Diabetes Mellitus, insulin-resistant, withacanthosis nigricans and hypertension; colon cancer; Inflammatory boweldisease), HNF4 alpha (Type II Diabetes), and ERa (Osteoporosis, Breastcancer). In particular embodiments, the active agent effective in thetreatment of a nuclear receptor-mediated disorder is the proteindeficient in the above-mentioned diseases, or a nucleic acid thatup-regulates its expression. Those of the above diseases that are causedby inappropriately high expression of the mutant gene may be treated byadministering a nucleic acid that down-regulates its expression.

In some aspects, a skeletal muscle disorder may be treated by alteringthe activity and/or levels of an orphan nuclear receptor. Orphan nuclearreceptors and diseases associated with them are known in the art, forexample in Smith et al., “Orphan Nuclear Receptors: therapeuticopportunities in skeletal muscle” Am J Physiol Cell Physiol 291:203-217,2006. For example, dysfunction of LXR-α, LXR-β, farnesoid X receptor(FXR), PPAR-α, -β/δ, and -γ, liver receptor homolog-1, and the smallheterodimeric partner can cause dyslipidemia, diabetes, obesity,inflammation, and cardiovascular disease. In addition, ERR-α, ROR-α,Rev-erb -α and -β, and Nur77 control several processes including lipidabsorpotion, lipolysis, inflammation, and myokine expression.Specifically, PPAR-δ coordinates glucose tolerance, fatty acidoxidation, and energy expenditure in skeletal muscle as well as inadipose tissue. PPAR-A regulates fatty acid oxidation, and stimulatesmitochondrial β-oxidation and thermogenesis in the muscles. In addition,LXR-α and -β regulate lipid metabolism in skeletal muscle. ERR-α, -β,and -γ are involved in ovesity, lipid metabolism, and oxidativephosphorylation, and mitochondrial respiration in skeletal and cardiacmuscle. Also, ROR nuclear receptors (including ROR-α1, -α2, α3, and -αα)are involved in muscle dysfunction such as ataxia, as well asdyslipidemia, atherosclerosis, and hypersensitive inflammatory response.Rev-erbs (including Rev-erbα and Rev-erbβ) are also involved indyslipidemia. In addition, the NR4A family (including Nurr1, Nur11, andNOR-1) is thought to be involved in obesity, energy balance,homeostasis, lipid utilization, and lipid and carbohydrate homeostasis.Based on the disclosures herein in combination with the state of theart, one of skill in the art will recognize which orphan nuclearreceptor protein, orphan nuclear receptor-modulating nucleic acid, ororphan nuclear receptor agonist or antagonist, may be administered inconjunction with the methods and compositions herein, in order toeffectively treat an orphan nuclear receptor-mediated disease.

In certain embodiments the compositions and methods herein may be usedto treat a disease or disorder involving dysfunction of factorscontrolling chromatin modification, and the conjugate is transportedinto cells in which altered chromatin modification state is desired. Incertain embodiments, the chromatin modification factors are histonedeacetylases, histone methyltransferases, histone kinases, histonephosphatases, histone ubiquitinylating enzymes, or histonepoly-ADP-ribosylases. Also, chromatin assembly factors and nucleosomeremodeling factors (and nucleic acids modulating their expression) maybe administered. In certain embodiments, DNA methyltransferases (such asDNMT1, DNMT2, DNMT3) or nucleic acids modulating their expression may beadministered in order to treat diseases associated with altered DNAmethyltransferase function, such as ICF Syndrome.

In certain embodiments, the disease or disorder involves incorrecthormone levels. The hormone levels may be inappropriately high or low.If the disease is associated with low hormone levels, one may administera gene (or gene product) in the synthesis pathway for that hormone. Forexample, to treat low testosterone levels, a gene or gene product of 17βhydroxysteroid dehydrogenase, 3β hydroxysteroid dehydrogenase, or 17,20lyase may be administered. Alternatively, if the disease is associatedwith elevated hormone levels, a nucleic acid (such as a siRNA) designedto reduce levels of the hormone synthesis pathway components may beadministered. Hormones include testosterone, estrogen, estradiol, andprogesterone.

In certain embodiments, the methods herein may be used to targettherapeutic antibodies, or nucleic acids encoding them, to particulartarget cells. The antibodies may be, for example, monoclonal antibodies,polyclonal antibodies, single-chain antibodies, or bi-specificantibodies. Suitable therapeutic antibodies include, but are not limitedto, Anti_EGFr antibodies (e.g., panitumamab, Erbitux (cetuximab),matuzumab, IMC-IIF 8, TheraCIM hR3), denosumab, Avastin (bevacizumab),Anti-HGF antibodies, Humira (adalimumab), Anti-Ang-2 antibodies,Herceptin (trastuzumab), Remicade (infliximab), Anti-CD20 antibodies,rituximab, Synagis (palivizumab), Mylotarg (gemtuzumab oxogamicin),Raptiva (efalizumab), Tysabri (natalizumab), Zenapax (dacliximab),NeutroSpec (Technetium (^(99m)Tc) fanolesomab), tocilizumab, ProstaScint(Indium-Ill labeled Capromab Pendetide), Bexxar (tositumomab), Zevalin(ibritumomab tiuxetan (IDEC-Y2B8) conjugated to yttrium 90), Xolair(omalizumab), MabThera (Rituximab), ReoPro (abciximab), MabCampath(alemtuzumab), Simulect (basiliximab), LeukoScan (sulesomab), CEA-Scan(arcitumomab), Verluma (nofetumomab), Panorex (Edrecolomab),alemtuzumab, CDP 870, and natalizumab.

In certain embodiments, the therapeutic agent is a proteasome inhibitor.Proteasome inhibitors may be used, for example, in the treatment ofinfectious diseases like HIV/AIDS and Hepatitis C, and for cancertherapy. In certain embodiments, the protease inhibitor is an antibodythat binds a protease.

In certain embodiments, the subject conjugates can be used to deliver anexpression construct to cells, such as muscle cells, that encodes atherapeutic protein. For instance, the expression construct can encode atherapeutic protein that is secreted by the transduced cell. Forexample, the expression construct acid can encode an angiogenic growthfactor such as VEGF, a fibroblast growth factor such as basic FGF orFGF-4, placental growth factor, hepatocyte growth factor, angiogenin,angiopoietin-1, pleiotrophin, transforming growth factor (α or β), ortumor necrosis factor α. The expression construct also can encode anatiuretic peptide such as an atrial natiuretic peptide (ANP) or a brainnatriuretic peptide (BNP), prostacyclin synthase, nitric oxide synthase,angiostatin, endostatin, erythropoietin (EPO), blood factors (such ascoagulation factors like Factor I, II, III, IV, V, VII, VIII, IV, X, XI,XII and XIII), GM-CSF, or an interleukin such as IL-1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. The expression constructcan encode an adhesion molecule such as a selectin (e.g., E, L, or Pselectin), an extracellular matrix protein (e.g., collagen type I, III,or IV; fibronectin; laminin; or vitronectin), an integrin (e.g., α₅β₁),or an intracellular adhesion molecule such as ICAM or a vascular celladhesion molecule (VCAM).

In either case, the expression construct that is delivered typically ispart of a vector in which a regulatory element such as a promoter isoperably linked to the nucleic acid of interest. The promoter can beconstitutive or inducible. Non-limiting examples of constitutivepromoters include cytomegalovirus (CMV) promoter and the Rous sarcomavirus promoter. As used herein, “inducible” refers to both up-regulationand down regulation. An inducible promoter is a promoter that is capableof directly or indirectly activating transcription of one or more DNAsequences or genes in response to an inducer. In the absence of aninducer, the DNA sequences or genes will not be transcribed. The inducercan be a chemical agent such as a protein, metabolite, growth regulator,phenolic compound, or a physiological stress imposed directly by, forexample heat, or indirectly through the action of a pathogen or diseaseagent such as a virus. The inducer also can be an illumination agentsuch as light and light's various aspects, which include wavelength,intensity, fluorescence, direction, and duration.

An example of an inducible promoter is the tetracycline (tet)-onpromoter system, which can be used to regulate transcription of thenucleic acid. In this system, a mutated Tet repressor (TetR) is fused tothe activation domain of herpes simplex VP 16 (transactivator protein)to create a tetracycline-controlled transcriptional activator (tTA),which is regulated by tet or doxycycline (dox). In the absence ofantibiotic, transcription is minimal, while in the presence of tet ordox, transcription is induced. Alternative inducible systems include theecdysone or rapamycin systems. Ecdysone is an insect molting hormonewhose production is controlled by a heterodimer of the ecdysone receptorand the product of the ultraspiracle gene (USP). Expression is inducedby treatment with ecdysone or an analog of ecdysone such as muristeroneA.

Additional regulatory elements that may be useful in vectors, include,but are not limited to, polyadenylation sequences, translation controlsequences (e.g., an internal ribosome entry segment, IRES), enhancers,or introns. Such elements may not be necessary, although they mayincrease expression by affecting transcription, stability of the mRNA,translational efficiency, or the like. Such elements can be included ina nucleic acid construct as desired to obtain optimal expression of thenucleic acids in the cell(s). Sufficient expression, however, maysometimes be obtained without such additional elements.

Vectors also can include other elements. For example, a vector caninclude a nucleic acid that encodes a signal peptide such that theencoded polypeptide is directed to a particular cellular location (e.g.,a signal secretion sequence to cause the protein to be secreted by thecell) or a nucleic acid that encodes a selectable marker. Non-limitingexamples of selectable markers include puromycin, adenosine deaminase(ADA), aminoglycoside phosphotransferase (neo, G418, APH), dihydrofolatereductase (DHFR), hygromycin-B-phosphtransferase, thymidine kinase (TK),and xanthin-guanine phosphoribosyltransferase (XGPRT). Such markers areuseful for selecting stable transformants in culture.

Viral vectors can be used to form the conjugates, and includeadenovirus, adeno-associated virus (AAV), retroviruses, lentiviruses,vaccinia virus, measles viruses, herpes viruses, and bovine papillomavirus vectors. See, Kay et al. (1997) Proc. Natl. Acad. Sci. USA94:12744-12746 for a review of viral and non-viral vectors. Viralvectors are modified so the native tropism and pathogenicity of thevirus has been altered or removed. The genome of a virus also can bemodified to increase its infectivity and to accommodate packaging of thenucleic acid encoding the polypeptide of interest.

Non-viral vectors can also be used in the subject conjugates.

To further illustrate, in one embodiment, the mammalian serum proteinthat is encoded by the vector is selected from the group consisting of atissue-type plasminogen activator, a receptor of a tissue-typeplasminogen activator, a streptokinase, a staphylokinase, a urokinase,and coagulation factors. The invention also provides a method fortreating associated with the formation of clots in its circulation,including the step of administering to the mammal a conjugate thatcauses the recombinant expression and secretion into the blood, such asfrom transduced muscle cells, of a therapeutically effective amount ofsuch a mammalian serum protein.

In another embodiment, the mammalian serum protein isglucocerebrosidase. The invention also provides a method of treating apatient having Gaucher disease, including the step of administering tothe patient a conjugate that causes the recombinant expression andsecretion into the blood, such as from transduced muscle cells, of atherapeutically effective amount of glucocerebrosidase.

In still another embodiment, the mammalian serum protein isα-galactosidase A. The invention also provides a method of treating amammal having Fabry disease, including the step of administering to thepatient a conjugate that causes the recombinant expression and secretioninto the blood, such as from transduced muscle cells, of atherapeutically effective amount of α-galactosidase A.

In still another embodiment, the mammalian serum protein is a cytokine.The cytokine can be selected from the group consisting of IFN-α, IFN-β,IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12 andIL-15. The invention also provides a method of treating a mammal havingcancer or a bacterial or viral infection, including the step ofadministering to the mammal a conjugate that causes the recombinantexpression and secretion into the blood, such as from transduced musclecells, of a therapeutically effective amount of such a cytokine.

In still another embodiment, the mammalian serum protein is a peptidehormone. The peptide hormone can be selected from the group consistingof antimullerian hormone (AMH), adiponectin, adrenocorticotropic hormone(ACTH), angiotensinogen and angiotensin, antidiuretic hormone (ADH),atrial-natriuretic peptide (ANP), calcitonin, cholecystokinin (CCK),corticotropin-releasing hormone (CRH), erythropoietin (EPO), folliclestimulating hormone (FSH), gastrin, glucagon, gonadotropin-releasinghormone (GnRH), growth hormone-releasing hormone (GHRH), human chorionicgonadotropin (hCG), growth hormone (GH), insulin, insulin-like growthfactor (IGF), leptin, luteinizing hormone (LH), melanocyte stimulatinghormone (MSH or α-MSH), neuropeptide Y, oxytocin, parathyroid hormone(PTH), prolactin (PRL), relaxin, renin, secretin, somatostatin,thrombopoietin, thyroid-stimulating hormone (TSH), andthyrotropin-releasing hormone (TRH). The invention also provides amethod for hormone replacement therapy in a mammal, including the stepof administering to the mammal a conjugate that causes the recombinantexpression and secretion into the blood, such as from transduced musclecells, of a therapeutically effective amount of such a peptide hormone.

In still other embodiments, the subject conjugate can be selected toinclude an expression vector that causes the recombinant expression andsecretion into the blood, such as from transduced muscle cells, of anenzyme selected from the group consisting of L-asparagine,L-glutaminase-L-asparaginase, L-methioninase, L-phenylalanine,ammonialyase, L-arginase, L-tyrosinase, L-serine dehydratase,L-threonine deaminase, indolyl-3-alkane hydroxylase, neuraminidase,ribonuclease, a protease, pepsin, and a carboxypeptidase. Suchconstructs can be used as part of a treatment program for cancer.

In another embodiment, the subject conjugate can be selected to includean expression vector that causes the recombinant expression andsecretion into the blood of lysostaphin. The invention also provides amethod of treating a mammal having a bacterial infection, including thestep of administering such a conjugate.

In certain embodiments, the subject methods and compositions are used todeliver a prodrug of any of the drugs listed herein.

Pharmaceutical compositions including a disclosed conjugate may be usedin the methods described herein. Thus, in one embodiment, apharmaceutical composition including a conjugate present in an amounteffective to treat a disease or disorder affecting a tissue expressing anucleoside transport pathway in a subject is used in methods describedherein. In another embodiment, a pharmaceutical composition including aconjugate present in an amount effective to treat a disease or disorderof skeletal muscle in a subject is used in methods described herein. Inaddition to the conjugate, the pharmaceutical composition may alsocontain other therapeutic agents, and may be formulated, for example, byemploying conventional vehicles or diluents, as well as pharmaceuticaladditives of a type appropriate to the mode of desired administration(for example, excipients, preservatives, etc.) according to techniquesknown in the art of pharmaceutical formulation.

In certain embodiments, the compositions disclosed herein are formulatedwith additional agents that promote entry into the desired cell ortissue. Such additional agents include micelles, liposomes, anddendrimers.

The term “effective amount” of an active agent refers an amount that isnon-toxic to a subject or a majority or normal cells, but is an amountof the active agent that is sufficient to provide a desired effect(e.g., treatment of a skeletal muscle disorder, metabolic disorder,blood disorder, or cancer). This amount may vary from subject tosubject, depending on the species, age, and physical condition of thesubject, the severity of the disease that is being treated, theparticular conjugate, or more specifically, the particular active agentused, its mode of administration, and the like. Therefore, it isdifficult to generalize an exact “effective amount,” yet, a suitableeffective amount may be determined by one of ordinary skill in the art.

The term “pharmaceutically acceptable” refers to the fact that thecarrier, diluent or excipient must be compatible with the otheringredients of the formulation and not deleterious to the recipientthereof. For example, the carrier, diluent, or excipient or compositionthereof may be administered to a subject along with a conjugate of theinvention without causing any undesirable biological effects orinteracting in an undesirable manner with any of the other components ofthe pharmaceutical composition in which it is contained.

Pharmaceutical compositions including the conjugate may be administeredby any suitable means, for example, parenterally, such as bysubcutaneous, intravenous, intramuscular, intrathecal, or intracisternalinjection or infusion techniques (e.g., as sterile injectable aqueous ornon-aqueous solutions or suspensions) in dosage formulations containingnon-toxic, pharmaceutically acceptable vehicles or diluents. In certainembodiments the conjugate is administered parenterally, or morepreferably, intravenously.

The mode of delivery chosen for administration of conjugates accordingto the present invention to a subject, such as a human patient ormammalian animal, will depend in large part on the particular activeagent present in the conjugate and the target cells. In general, thesame dosages and administration routes used to administer the activeagent alone will also be used as the starting point for the conjugate.However, it is preferred that smaller doses be used initially due to theexpected increase in cellular penetration of the active agent. Theactual final dosage for a given route of administration is easilydetermined by routine experimentation. In general the same proceduresand protocols that have been previously used for other antibody-basedtargeting conjugates (e.g., parenterally, intravenous, intrathecal, andthe like) are also suitable for the conjugates of the present invention.

The pharmaceutical compositions of the conjugate can be administeredeither alone or in combination with other therapeutic agents, mayconveniently be presented in unit dose form and may be prepared by anyof the methods well known in the art of pharmacy. All methods includebringing the conjugate into association with the carrier, whichconstitutes one or more accessory ingredients. In general, thepharmaceutical compositions are prepared by uniformly and intimatelybringing the active ingredient into association with a liquid carrier.In a pharmaceutical composition, the conjugate is included in an amountsufficient to produce the desired effect upon the process or conditionof disease.

Depending on the condition being treated, these pharmaceuticalcompositions may be formulated and administered systemically or locally.Techniques for formulation and administration may be found in the latestedition of “Remington's Pharmaceutical Sciences” (Mack Publishing Co,Easton Pa.). Suitable routes may, for example, parenteral delivery,including intramuscular, subcutaneous, intramedullary, intrathecal,intraventricular, intravenous, or intraperitoneal. For injection, thepharmaceutical compositions of the invention may be formulated inaqueous solutions, preferably in physiologically compatible buffers suchas Hanks' solution, Ringer's solution, or physiologically bufferedsaline.

The present disclosure also provides a pharmaceutical compositionincluding a conjugate described herein and an agent that promotes ENT2expression in a tissue. In some aspects, the agent that promotes ENT2expression in a tissue is an agent that inhibits hypoxia or an agentthat inhibits HIF-1. The tissue may be a hypoxic tissue, such as ahypoxic tumor, a tissue with insufficient vasculature, an ulcer, adiabetic ulcer, a poorly-healing wound, an ischemic area, an ischemicarea resulting from stroke, or an ischemic area resulting fromcardiovascular disease. In certain embodiments, the agent that inhibitsHIF-1α is a siRNA, an RNAi construct, a hairpin RNA, or a miRNA thatreduces HIF-1α expression. In some embodiments, the HIF-1α inhibitor isa chemotherapeutic drug, topotecan, NSC 644221, PX-478, YC-1,17-AAG, orbevacizumab. In certain embodiments, the agent that inhibits hypoxia isan agent that normalizes tumor vasculature, or an agent that alters theredox state of a tissue. The agent that inhibits hypoxia may be excessoxygen, TSC, or almitrine. Excess oxygen may be delivered, for example,by intubation, an oxygen mask, or a hyperbaric chamber. In certainembodiments, the agent that promotes ENT2 expression is an inhibitor ofa gene that downregulates ENT2, such as HIF-1α. In other embodiments,the agent that promotes ENT2 expression is a nucleic acid encoding ENT2,for example an expression construct that drives expression of ENT2 orany fragment thereof having essentially the same therapeutic transportactivity as full-length ENT2.

Furthermore, herein is provided a method of treating an ENT-2 deficienttissue, wherein the method includes: a) administering an agent thatpromotes ENT2 expression and/or activity, and b) administering one ofthe conjugates disclosed herein.

In certain aspects, a conjugate as described herein may be adminsteredtogether with ATP or an ATP-generating agent. These agents may be usedto inhibit hypoxia and/or ischemia In certain aspects, ATP isspecifically delivered to the target tissue, for example, usingliposomes. Methods of delivering ATP to ischemic tissue are known in theart, and are described in U.S. Pat. No. 7,056,529 and Verma D et al.,“ATP-loaded Liposomes Effectively Protect Mechanical Functions of theMyocardium from Global Ischemia in an Isolated Rat Heart Model”, JControl Release. 2005 Nov. 28; 108(2-3): 460-471.

In certain embodiments, a patient is treated with a hypoxia-inhibitingagent and a conjugate herein prior to surgery, as a prophylactictreatment for ischemia caused by surgery.

A number of drugs affect tumor vasculature. While the mechanism of suchdrugs is not fully understood, there appear to be three broad classes ofvasculature-targeting agents. First, an agent may be anti-angiogenic.Such agents prevent the growth of new blood vessels, starving the tumorof blood and oxygen. Such agents make a tumor more hypoxic. Second, anagent may collapse pre-existing tumor vasculature, also increasing thehypoxia of the tumor. Third, vasculature-normalizing agents reduce theabnormalities of the tumor vasculature. For example, they may reduce thenumber of excess epithelial cells in the tumor vasculature. These agentsimprove blood flow to the tumor and reduce hypoxia. Paradoxically,vasculature-normalizing agents may be used to impede tumor growth, byallowing other therapeutic molecules (such as chemotherapeutic drugs)better access to the tumor.

Some therapies previously thought to be anti-angiogenic may insteadproduce vasculature normalization. For example, one may block vascularendothelial growth factor (VEGF) or its receptor (VEGFR2), causingapoptosis of endothelial cells. Consequently there is a decrease inblood vessel diameter, density and permeability. There is also adecrease in interstitial fluid pressure and, at least in some instances,elevated oxygen tension (reviewed in Jain R et al., Nature Medicine 7,987-989 (2001)). Various other therapeutics also contribute tovasculature normalization, including ST1571, C225, and Herceptin, whichblock PDGFR, HER1 and HER2 signaling, respectively.

Therapeutic antibodies may be used to normalize tumor vasculature. Forexample, a neutralizing antibody (A4.6.1) against VEGF/VPF is describedin Yuan F et al. (Proc Natl Acad Sci USA. 1996 Dec. 10;93(25):14765-70.) Permeabolization of the tumor vasculature was observeda few hours after injection and lasted about 5 days. Also, the (VEGFR)-2neutralizing antibody DC101 may be used to normalize tumor vasculatureas described in Kadambi et al., (Cancer Res. 2001 Mar. 15;61(6):2404-8). Humanized versions of these antibodies, and antibodyvariants such as single-chain antibodies, may be used in accordance withthe methods disclosed herein.

The invention will now be described in greater detail by reference tothe following non-limiting examples.

EXAMPLE 1

The anti-DNA antibody fragment 3E10 Fv has received attention as a novelmolecular delivery vehicle due to its penetration into living cells withspecific nuclear localization, absence of toxicity, and successfuldelivery of therapeutic cargo proteins in vitro and in vivo. In thepresent study, the pathway that allows 3E10 Fv to cross cell membraneswas elucidated. In particular, the present study demonstrates that 3E10Fv penetrates cells through a nucleoside salvage transporter. Theresults showed that 3E10 Fv is unable to penetrate into cells deficientin the equilibrative nucleoside transporter, ENT2, and reconstitution ofENT2 into ENT2-deficient cells restores 3E10 Fv transport into cellnuclei. These results represented the first demonstration of proteintransport through a nucleoside salvage pathway.

Cell Lines.

COS-7, K562, and CEM/ENT1 cells were purchased from the American TypeCulture Collection (Rockville, Md.). A nucleoside transport-deficientporcine kidney tubular epithelial cells (PKNTD) were generated andtransfected with plasmids containing nucleic acid encoding hENT1 orhENT2 to form PKNTD/ENT1 and PKNTD/ENT2 cells, respectively, aspreviously described (Ward et al., J. Biol. Chem. 275:8375-81, 2000).

Plasmids.

A construct for expression of 3E10 Fv in the X-33 strain of Pichiapastoris, pPICZαA-Fv, was generated by ligating cDNA encoding thesingle-chain Fv fragment of mAb 3E10 into pPICZαA, as previouslydescribed (Weisbart et al., Cancer Lett. 195:211-9, 2003; and Weisbartet al., Int J Oncol 2004; 25:1113-8).

Purification of 3E10 Fv. 3E10 Fv was purified from the supernatant of P.pastoris transfected with pPICZαA-Fv as previously described (Weisbartet al., Cancer Lett. 195:211-9, 2003).

Cellular Penetration Assays.

Purified 3E10 Fv was exchange-dialyzed into PBS prior to application tocells. After dialysis, 10% fetal calf serum was added to the buffercontaining the 3E10 Fv. Control buffer was PBS with 10% fetal calfserum. For adherent cell lines (COS-7, PKNTD/ENT1, and PKNTD/ENT2), 50μL of control buffer or 3E10 Fv in PBS+10% fetal calf serum was added tocells on 96-well plates for one hour. After incubation with 3E10 Fv, theantibody fragment was removed and cells were washed, fixed in chilled100% ethanol, and stained with the 9E10 α-myc antibody as previouslydescribed (Weisbart et al., Cancer Lett. 195:211-9, 2003). Fornon-adherent cells (K562 and CEM/ENT1) cell pellets composed of ˜200,000cells were re-suspended in 100 μL control buffer or 10 μM 3E10 Fv andallowed to incubate with intermittent shaking at 37° C. for one hour.Cells were then centrifuged at 100 g for 2 minutes and washed threetimes with PBS. Next, cells were spread on glass slides and allowed todry overnight. Cells were then fixed in chilled 100% ethanol for tenminutes, washed three times in PBS, and stained with the 9E10 α-mycantibody.

Nucleoside Transporter Inhibition Assay.

Nitrobenzylmercaptopurine riboside (NBMPR) was purchased from Sigma (St.Louis, Mo.), and a stock solution of 100 mM NBMPR in DMSO was prepared.To control for the effects of DMSO in cell culture, DMSO was added tocontrol buffers not containing NBMPR. The concentration of DMSO in allcontrol and experimental buffers was 0.1%. COS-7 cells were pre-treatedfor 30 minutes with control buffer (PBS+10% fetal calf serum) or buffercontaining 10 μM or 100 μM NBMPR. Buffers were then replaced withcontrol buffer or 10 μM 3E10 Fv in the presence or absence of 10 μM or100 μM NBMPR for one hour. Cells were then washed, fixed, and stainedwith the 9E10 α-myc antibody.

Microscopic Images.

Images of cells were acquired with an Olympus IX70 inverted microscopewith RC reflected light fluorescent attachment and MagnaFire SP DigitalImaging System (Olympus, Melville, N.Y.) as described previously(Weisbart et al., J Immunol 164:6020-6, 2000). Scale bar in cellimages=5 μm.

The single chain Fv fragment of the 3E10 anti-DNA autoantibody (3E10 Fv)has recently been harnessed as a novel molecular delivery vehicle due toits specific nuclear localization and apparent lack of toxicity(Weisbart et al., J. Autoimmun. 11(5), 539-46, 1998). 3E10 Fv andFv-fusion proteins readily transduce across cell membranes and penetrateinto cell nuclei, and 3E10 Fv has successfully delivered biologicallyactive proteins such as Hsp70 (Hansen et al., Brain Res. 1088(1),187-96, 2006) and p53 (Weisbart et al., Int. J. Oncol. 25(6), 1867-1873,2004) into living cells in vitro. Moreover, 3E10 Fv mediated full-lengthp53 protein therapy in vivo (Hansen et al., Cancer Res. 67(4), 1769-74,2007). The pathway that carries 3E10 Fv across cell membranes and intocell nuclei, however, has not been identified previously.

Previous studies implicated DNA binding as important in 3E10 Fvtransduction into cell nuclei. Specifically, mutations that abrogate DNAbinding by the antibody render it incapable of cellular penetration(Zack et al., J. Immunol. 157(5), 2082-8, 1996). The association betweencellular penetration and DNA binding distinguished 3E10 Fv from otherprotein transduction domains and suggested the potential involvement ofnucleoside salvage pathways in 3E10 Fv transport. Both concentrative(CNT) and equilibrative (ENT) nucleoside transporters mediate the uptakeof nucleosides and nucleobases by mammalian cells (Kong et al., Curr.Drug Metab. 5(1):63-84, 2004). Other studies demonstrating 3E10 Fvpenetration into COS-7 cells that lack endogenous CNTs, suggested thatCNTs do not play a major role in 3E10 Fv transport (Hansen et al., BrainRes. 1088(1), 187-96, 2006; and Toan et al., Pflugers Arch. 447(2),195-204, 2003). Thus, the role of ENTs in 3E10 Fv transport was examinedin the present study.

ENT1 and ENT2, which each mediate equilibrative nucleoside transport inmammalian cells, are inhibited by high concentrations of NBMPR (Ward etal., J. Biol. Chem. 275(12):8375-81, 2000). NBMPR was tested forinhibition of 3E10 Fv transport. Purified 3E10 Fv (constructed with His₆tag for purification and myc tag for identification) migrated as asingle ˜30 kDa protein on SDS-PAGE. Transduction of 3E10 Fv into COS-7cells was confirmed by incubating cells with 10 μM 3E10 Fv for one hourat 37° C., followed by Western blot analysis of cell lysates orimmunocytochemical staining of cells (FIG. 1C, top panels). Western blotanalysis of cell lysates demonstrated the presence of a ˜30 kDamyc-tagged protein inside cells treated with 3E10 Fv, which indicatedpenetration of the full-length antibody fragment. Furthermore,immunocytochemical staining confirmed nuclear localization by 3E10 Fv(FIG. 1C, top right panel), consistent with previous confocal microscopyand immunocytochemical studies on the antibody (Hansen et al., BrainRes. 1088(1), 187-96, 2006; and Weisbart et al., J. Immunol. 164(11),6020-6, 2000). Next, COS-7 cells were pre-treated for 30 minutes withcontrol buffer or buffer containing 100 μM NBMPR prior to a one hourincubation with 10 μM 3E10 Fv in the presence or absence of NBMPR.Subsequent immunocytochemical staining of the cells demonstrated that100 μM NBMPR suppressed nuclear penetration by 3E10 Fv (FIG. 1C, bottomleft panel), which suggested that ENT1 or ENT2 is involved in 3E10 Fvtransport.

To resolve which of the ENTs was linked to 3E10 Fv transport, 3E10 Fvpenetration into COS-7 cell nuclei was tested in the presence of a lowerdose of NBMPR to take advantage of the different K_(i) of NBMPR for ENT1and ENT2 (0.4 nM versus 2.8 μM, respectively) (Ward et al., J. Biol.Chem. 275(12):8375-81, 2000). Thus, at 10 μM NBMPR ENT1 activity iscompletely inhibited while ENT2 retains moderate activity. In contrastto the distinct inhibition of 3E10 Fv transport provided by 100 μM NBMPR(FIG. 1C, bottom left panel), 3E10 Fv successfully penetrated COS-7 cellnuclei in the presence of 10 μM NBMPR (FIG. 1C, bottom right panel).This result suggested that ENT2, not ENT1, mediated transport of 3E10Fv. The decreased nuclear staining intensity in cells treated with 3EI 0Fv+10 μM NBMPR compared to cells treated with 3E10 Fv alone likelyreflects partial inhibition of 3E10 Fv transport due to theexpected >50% suppression of ENT2 activity by 10 μM NBMPR.

As an additional approach to identifying the equilibrative nucleosidetransporter(s) involved in 3E10 Fv transduction, 3E10 Fv transductioninto the CEM/ENT1 cell line that expresses ENT1 but lacks ENT2 (Crawfordet al., J. Biol. Chem. 273(9), 5288-93, 1998) was examined. K562leukemia cells, which express both ENT1 and ENT2 (Huang et al.,Nucleosides Nucleotides Nucleic Acids 23(8-9), 1445-50, 2004), were usedas a positive control. CEM/ENT1 cells (which express ENT1 but not ENT2)and K562 cells were incubated with control buffer or 10 μM 3E10 Fv forone hour. Cells were then washed, fixed, and stained with the α-mycantibody. Control K562 cells and CEM/ENT1 cells showed no staining.Consistent with the studies in COS-7 cells, immunocytochemical stainingof the 3E10 Fv-treated K562 cells demonstrated penetration of theantibody fragment into 100% of the cells. CEM/ENT1 cells treated with3E10 Fv, however, showed no staining. This result demonstrated thatabsence of ENT2 significantly impaired transduction by 3E10 Fv intocells. Taken together, the inhibition of 3E10 Fv transport by highconcentrations of NBMPR and failure of 3E10 Fv to penetrate a cell linelacking ENT2 strongly support a role of ENT2 in 3E10 Fv transport.

To verify that ENT2 facilitates 3E10 Fv intranuclear proteintransduction, experiments were performed on nucleosidetransporter-deficient PK15 cells (PKNTD) with either ENT1 or ENT2reconstituted through stable transfection and expression of ENT1 or ENT2cDNA (Ward et al., J. Biol. Chem. 275(12):8375-81, 2000). PKNTD/ENT1 andPKNTD/ENT2 cells were treated with control buffer (i.e., control cells)or 10 μM 3E10 Fv for one hour. Cells were then washed, fixed, andstained with the α-myc antibody. Control PKNTD/ENT1 and PKNTD/ENT2 cellsshowed an absence of staining. Similarly, PKNTD/ENT1 cells treated forone hour with 10 μM 3E10 Fv showed an absence of staining, exhibiting noevidence of nuclear penetration, which indicated a failure of theantibody fragment to penetrate the ENT2-deficient cells. This result wasconsistent with the results obtained with the CEM/ENT1 cells. Incontrast, 3E10 Fv-treated PKNTD/ENT2 cells exhibited distinct nuclearstaining, which indicated that restoration of ENT2 to the nucleosidetransporter deficient cells significantly augmented nuclear penetrationby 3E10 Fv. This result confirmed that the presence of ENT2 facilitatesnuclear penetration by 3E10 Fv and verified protein transduction of theantibody fragment through the ENT2-mediated nucleoside salvage pathway.

The nucleoside salvage pathways have been studied in detail, but proteintransport through or related to nucleoside salvage has not beenpreviously described. While not wishing to be bound by any particulartheory, 3E10 Fv may be carried into cells by virtue of its binding tonucleosides or nucleobases that are subsequently transported into cellsby ENT2. Alternatively, 3E10 Fv may mimic the structure of a nucleosideor nucleobase that is recognized and transported into cells by ENT2.Elucidation of the specific mechanism by which ENT2 facilitates 3E10 Fvtransport should yield further insights into both protein transductionand nucleoside salvage pathways. Furthermore, since ENT2 is located inboth plasma and nuclear membranes, it will be important to ascertainwhether ENT2 facilitates transport of 3E10 Fv across both cellular andnuclear membranes or if another pathway is involved in nuclearpenetration (Mani et al., J. Biol. Chem. 273(46), 30818-325, 1998).

With regard to molecular therapy, the linkage between ENT2 and nuclearpenetration by 3E10 Fv reported herein further establishes 3E10 Fv as anovel molecular delivery vehicle that is distinct from other proteintransduction domains previously described. Endosomal localization bycell-penetrating peptides limits their role in molecular therapy (Joneset al., Br. J. Pharmacol. 145(8), 1093-102, 2005; and Kaplan et al., J.Control Release 102(1):247-53, 2005), but the identification of 3E10 Fvtransport through ENT2 provides a rationale for future studies on theuse of 3E10 Fv in delivering molecules such as siRNAs, antisenseoligonucleotides, and transcription factors to cell nuclei.

Moreover, it is possible that toxic cell-penetrating antibodies utilizea nucleoside salvage pathway in cellular penetration. Thus, inhibitionof nucleoside transporters may be a means of limiting tissue damage bycytotoxic autoantibodies in certain autoimmune diseases. The discoveryof intranuclear protein transduction by 3E10 Fv through theENT2-mediated nucleoside salvage pathway has profound implications forcell biology, pharmacology, and medicine.

Although the invention has been described with reference to the aboveexample, it will be understood that modifications and variations areencompassed within the spirit and scope of the invention. Accordingly,the invention is limited only by the following claims.

1. A conjugate comprising: a substrate that is capable of beingtransported by a nucleoside transport pathway, with the proviso thatwhen the substrate is an antibody, it is not the monoclonal antibody3E10 or a fragment thereof, and an active agent linked to the substrate,wherein the conjugate is transported by the nucleoside transportpathway.
 2. A conjugate according to claim 1, wherein the nucleosidetransport pathway comprises an equilibrative nucleoside transporter or aconcentrative nucleoside transporter.
 3. A conjugate according to claim2, wherein the equilibrative nucleoside transporter is insensitive tolow concentrations of nitrobenzylmercaptopurine riboside (NBMBR).
 4. Aconjugate according to claim 2, wherein the equilibrative nucleosidetransporter is selected from the group consisting of ENT1, ENT2, ENT3,and ENT4.
 5. A conjugate according to claim 1, wherein the substrate isselected from the group consisting of a nucleoside, a nucleobase, anucleotide, a nucleoside analog, an oligonucleotide, a peptide, apolypeptide, an antibody, an antibody fragment.
 6. A conjugate accordingto claim 1, wherein the substrate is an antibody or a fragment thereof.7. A conjugate according to claim 4, wherein the antibody or fragmentthereof binds nucleic acid.
 8. A conjugate according to claim 1, whereinthe active agent is selected from the group consisting of a nucleicacid, an inorganic molecule, an organic molecule, a small organicmolecule, a drug compound, a peptide, a polypeptide, an antibody, anantibody fragment, a peptidomimetic, DNA, RNA, a ribozyme, hairpin RNA,siRNA, miRNA, an antagomir, a PNA, a LNA.
 9. A conjugate according toclaim 8, wherein the drug compound is selected from the group consistingof α-glucosidase, α-L-iduronidase, α-galactosidase A, arylsulfatase,N-acetylgalactosamine-6-sulfatase or β-galactosidase, iduronate2-sulfatase, ceramidase, galactocerebrosidase, β-glucuronidase, HeparanN-sulfatase, N-Acetyl-α-glucosaminidase, Acetyl CoA-α-glucosaminideN-acetyl transferase, N-acetyl-glucosamine-6 sulfatase, Galactose6-sulfatase, Arylsulfatase A, B, or C, Arylsulfatase A Cerebroside,Ganglioside, Acid β-galactosidase G_(MI) Gaiglioside, Acidβ-galactosidase, Hexosaminidase A, Hexosaminidase B, α-fucosidase,α-N-Acetyl galactosaminidase, Glycoprotein Neuraminidase,Aspartylglucosamine amidase, Acid Lipase, Acid Ceramidase, LysosomalSphingomyelinase, other Sphingomyelinase, dystrophin, components ofdystrophin-glycoprotein complex, the laminin-α2 chain, fukutin-relatedprotein, LARGE, fukutin, EMD, LMNA, DMPK, ZNF9, and PABPN1, Glycogensynthase, Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase.
 10. A method of delivering a conjugate to atarget cell expressing a nucleoside transport pathway comprising,contacting the target cell expressing the nucleoside transport pathwaywith a conjugate comprising, a substrate that is capable of beingtransported by the nucleoside transport pathway, with the proviso thatwhen the substrate is an antibody, it is not the monoclonal antibody3E10 or a fragment thereof, and an active agent linked to the substrate,wherein the conjugate is transported by the nucleoside transportpathway, thereby transporting the conjugate into the target cell.
 11. Amethod according to claim 9, wherein the nucleoside transport pathwaycomprises an equilibrative nucleoside transporter or a concentrativenucleoside transporter.
 12. A method according to claim 10, wherein theequilibrative nucleoside transporter is insensitive to inhibition by lowconcentrations of nitrobenzylmercaptopurine riboside (NBMBR).
 13. Amethod according to claim 10, wherein the equilibrative nucleosidetransporter is selected from the group consisting of ENT1, ENT2, ENT3,and ENT4.
 14. A method according to claim 10, wherein the substrate isselected from the group consisting of a nucleoside, a nucleobase, anucleotide, a nucleoside analog, an oligonucleotide, a peptide, anantibody, and an antibody fragment.
 15. A method according to claim 10,wherein the substrate is an antibody or a fragment thereof.
 16. A methodaccording to claim 15, wherein the antibody or fragment thereof bindsnucleic acid.
 17. A method according to claim 10, wherein the activeagent is selected from the group consisting of a nucleic acid, aninorganic molecule, an organic molecule, a small organic molecule, adrug compound, a peptide, a polypeptide, an antibody, an antibodyfragment, a peptidomimetic, a lipid, DNA, RNA, a ribozyme, hairpin RNA,siRNA, miRNA, an antagomir, a PNA, a LNA.
 18. A method according toclaim 17, wherein the drug compound is selected from the groupconsisting of α-glucosidase, α-L-iduronidase, α-galactosidase A,arylsulfatase, N-acetylgalactosamine-6-sulfatase or β-galactosidase,iduronate 2-sulfatase, ceramidase, galactocerebrosidase,β-glucuronidase, Heparan N-sulfatase, N-Acetyl-α-glucosaminidase, AcetylCoA-α-glucosaminide N-acetyl transferase, N-acetyl-glucosamine-6sulfatase, Galactose 6-sulfatase, Arylsulfatase A, B, or C,Arylsulfatase A Cerebroside, Ganglioside, Acid β-galactosidase G_(MI)Gaiglioside, Acid β-galactosidase, Hexosaminidase A, Hexosaminidase B,α-fucosidase, α-N-Acetyl galactosaminidase, Glycoprotein Neuraminidase,Aspartylglucosamine amidase, Acid Lipase, Acid Ceramidase, LysosomalSphingomyelinase, other Sphingomyelinas, dystrophin, components ofdystrophin-glycoprotein complex, the laminin-α2 chain, fukutin-relatedprotein, LARGE, fukutin, EMD, LMNA, DMPK, ZNF9, and PABPN1, Glycogensynthase, Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase.
 19. A method according to claim 10, wherein thetarget cell is from a tissue selected from the group consisting ofmuscle, skeletal muscle, cardiac muscle, vascular endothelium, heart,brain, placenta, thymus, pancreas, prostate, kidney, blood, skin, andENT2-expressing cancer cells.
 20. A method of screening a conjugate fortransport by a nucleoside transport pathway comprising, contacting acell expressing the nucleoside transport pathway, with a conjugate undersuitable conditions for transport to occur; and determining whether theconjugate is transported into the cell by the nucleoside transportpathway.
 21. A method according to claim 20, wherein the nucleosidetransport pathway comprises an equilibrative nucleoside transporter or aconcentrative nucleoside transporter.
 22. A method according to claim21, wherein the equilibrative nucleoside transporter is insensitive tolow concentrations of nitrobenzylmercaptopurine riboside (NBMBR).
 23. Amethod according to claim 21, wherein the equilibrative nucleosidetransporter is selected from the group consisting of ENT1, ENT2, ENT3,and ENT4.
 24. A method according to claim 21, wherein the equilibrativenucleoside transporter is an ENT2 transporter.
 25. A method according toclaim 24, wherein the cell is transfected with DNA encoding the ENT2transporter.
 26. A method according to claim 25, wherein the determiningstep comprises comparing the amount of conjugate transported into thecell transfected with DNA encoding ENT2 to the amount of conjugatetransported into a control cell not transfected with ENT2, wherein anincrease in transport of conjugate of the transfected cell as comparedto the control cell indicates transport is by the ENT2 transporter. 27.A method according to claim 20, wherein transport of the conjugateoccurs in the presence of low concentrations of NBMPR.
 28. A methodaccording to claim 20, wherein the conjugate comprises a detectablelabel.
 29. A method of treating a skeletal muscle disorder comprising,administering to a patient having a skeletal muscle disorder a conjugatecomprising: a substrate that is capable of being transported by anequilibrative nucleoside transporter, and an active agent for treatingthe skeletal muscle disorder, wherein the active agent is linked to thesubstrate, and further wherein the conjugate is transported by theequilibrative nucleoside transporter, whereby the conjugate istransported into skeletal muscle cells, thereby delivering the activeagent.
 30. A method according to claim 29, wherein the skeletal muscledisorder is selected from the group consisting of Becker's musculardystrophy (BMD), Congenital muscular dystrophy, Duchenne musculardystrophy (DMD), Distal muscular dystrophy, Emery-Dreifuss musculardystrophy, Facioscapulohumeral muscular dystrophy (FSHD), Limb-girdlemuscular dystrophy (LGMD), Myotonic muscular dystrophy, Oculopharyngealmuscular dystrophy, Pompe Disease, Hurler Syndrome, Fabry Disease,Maroteaux-Lamy Syndrome, Morquio Syndrome, Hunter Syndrome, FarberDisease, Krabbe Disease, Sly Syndrome, Sanfilippo (including A, B, andD), Morquio A, Multiple Sulfatase Deficiency, MetachromaticLeukodystrophy, Mucolipidosis IV, G.sub.MI Gangliosidosis,Galactosialidosis, Tay-Sachs and Tay-Sachs Variants, Sandhoff,Fucsidosis, Schindler Disease, Sialidosis, Aspartylglucosaminuria,Wolman Disease, Farber Lipogranulomatosis, Nieman-Pick disease,Phosphorylase Deficiency, Acid Maltase Deficiency, MitochondrialMyopathy, Carnitine Palmityl Transferase Deficiency, PhosphoglycerateKinase Deficiency, and Phosphoglycerate Mutase Deficiency.
 31. A methodof treating a genetic disorder comprising, administering to a patienthaving a genetic disorder a conjugate comprising: a substrate that iscapable of being transported by an equilibrative nucleoside transporter,and an active agent for treating the genetic disorder, wherein theactive agent is linked to the substrate, and further wherein theconjugate is transported by the equilibrative nucleoside transporter,whereby the conjugate is transported into cells, thereby delivering theactive agent.
 32. The method of claim 31, wherein the active agent is agene or protein that is deficient in patients having the geneticdisease.
 33. A method of treating a cancer comprising, administering toa patient having cancer a conjugate comprising: a substrate that iscapable of being transported by an equilibrative nucleoside transporter,and an active agent for treating cancer, wherein the active agent islinked to the substrate, and further wherein the conjugate istransported by the equilibrative nucleoside transporter, whereby theconjugate is transported into cancerous cells, thereby delivering theactive agent.
 34. The method of claim 33, wherein the active agent is atumor suppressor gene or tumor suppressor protein.
 35. A methodaccording to claim 29, wherein the substrate is selected from the groupconsisting of a nucleoside, a nucleobase, a nucleotide, a nucleosideanalog, an oligonucleotide, a peptide, an antibody, and an antibodyfragment.
 36. A method according to claim 29, wherein the substrate isan antibody or a fragment thereof.
 37. A method according to claim 36,wherein the antibody or fragment thereof binds nucleic acid.
 38. Amethod according to claim 37, wherein the antibody or fragment thereofan antibody, variant thereof, or functional fragment thereof havingbinding specificity of an antibody as produced by the hybridoma havingATCC accession number PTA
 2439. 39. A method according to claim 29,wherein the active agent is selected from the group consisting ofα-glucosidase, α-L-iduronidase, α-galactosidase A, arylsulfatase,N-acetylgalactosamine-6-sulfatase or β-galactosidase, iduronate2-sulfatase, ceramidase, galactocerebrosidase, β-glucuronidase, HeparanN-sulfatase, N-Acetyl-α-glucosaminidase, Acetyl CoA-α-glucosaminideN-acetyl transferase, N-acetyl-glucosamine-6 sulfatase, Galactose6-sulfatase, Arylsulfatase A, B, or C, Arylsulfatase A Cerebroside,Ganglioside, Acid β-galactosidase G_(MI) Gaiglioside, Acidβ-galactosidase, Hexosaminidase A, Hexosaminidase B, α-fucosidase,α-N-Acetyl galactosaminidase, Glycoprotein Neuraminidase,Aspartylglucosamine amidase, Acid Lipase, Acid Ceramidase, LysosomalSphingomyelinase other Sphingomyelinase, dystrophin, components ofdystrophin-glycoprotein complex, the laminin-α2 chain, fukutin-relatedprotein, LARGE, fukutin, EMD, LMNA, DMPK, ZNF9, and PABPN1, Glycogensynthase, Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase.
 40. A method of treating an autoimmune disordercomprising, administering to a patient having an autoimmune disorder acompound that inhibits transport by an ENT2 transporter.
 41. Apharmaceutical composition comprising the conjugate of claim 1 and anagent that promotes ENT2 expression in a tissue.
 42. The pharmaceuticalcomposition of claim 41, wherein the agent that promotes ENT2 expressionin a tissue is an agent that treats or inhibits hypoxia or an agent thatinhibits HIF-1α.
 43. The pharmaceutical composition of claim 41, whereinthe tissue is hypoxic.
 44. The pharmaceutical composition of claim 44,wherein the tissue that is hypoxic is a hypoxic tumor, a tissue withinsufficient vasculature, an ulcer, an ischemic area resulting fromstroke, or an ischemic area resulting from cardiovascular disease. 45.The pharmaceutical composition of claim 42, wherein the agent thattreats or inhibits HIF-1α is topotecan, NSC 644221, PX-478, YC-1,17-AAG,bevacizumab, or a siRNA, an RNAi construct, a hairpin RNA, or miRNA thatreduces HIF-1α expression.
 46. The pharmaceutical composition of claim42, wherein the agent that treats or inhibits hypoxia is an agent thatnormalizes tumor vasculature, or an agent that alters the redox state ofa tissue.
 47. The pharmaceutical composition of claim 42, wherein theagent that treats or inhibits hypoxia is excess oxygen, TSC, almitrine,ATP, or an ATP-generating system.
 48. A method of treating an ENT-2deficient tissue, comprising: a) administering an agent that promotesENT2 expression and/or activity, and b) administering a conjugate ofclaim
 1. 49. A method according to claim 31, wherein the substrate isselected from the group consisting of a nucleoside, a nucleobase, anucleotide, a nucleoside analog, an oligonucleotide, a peptide, anantibody, and an antibody fragment.
 50. A method according to claim 31,wherein the substrate is an antibody or a fragment thereof.
 51. A methodaccording to claim 31, wherein the active agent is selected from thegroup consisting of α-glucosidase, α-L-iduronidase, α-galactosidase A,arylsulfatase, N-acetylgalactosamine-6-sulfatase or α-galactosidase,iduronate 2-sulfatase, ceramidase, galactocerebrosidase,α-glucuronidase, Heparan N-sulfatase, N-Acetyl-α-glucosaminidase, AcetylCoA-α-glucosaminide N-acetyl transferase, N-acetyl-glucosamine-6sulfatase, Galactose 6-sulfatase, Arylsulfatase A, B, or C,Arylsulfatase A Cerebroside, Ganglioside, Acid β-galactosidase G_(MI)Gaiglioside, Acid β-galactosidase, Hexosaminidase A, Hexosaminidase B,α-fucosidase, α-N-Acetyl galactosaminidase, Glycoprotein Neuraminidase,Aspartylglucosamine amidase, Acid Lipase, Acid Ceramidase, LysosomalSphingomyelinase other Sphingomyelinase, dystrophin, components ofdystrophin-glycoprotein complex, the laminin-α2 chain, fukutin-relatedprotein, LARGE, fukutin, EMD, LMNA, DMPK, ZNF9, and PABPN1, Glycogensynthase, Glucose-6-phosphatase, Debranching enzyme, Transglucosidase,Myophosphorylase, Phosphorylase, Phosphofructokinase, Acid MaltaseDeficiency, Carnitine Palmityl Transferase, Phosphoglycerate Kinase, orPhosphoglycerate Mutase.
 52. A method according to claim 33, wherein thesubstrate is selected from the group consisting of a nucleoside, anucleobase, a nucleotide, a nucleoside analog, an oligonucleotide, apeptide, an antibody, and an antibody fragment.
 53. A method accordingto claim 33, wherein the substrate is an antibody or a fragment thereof.54. A method according to claim 33, wherein the active agent is selectedfrom the group consisting of α-glucosidase, α-L-iduronidase,α-galactosidase A, arylsulfatase, N-acetylgalactosamine-6-sulfatase orβ-galactosidase, iduronate 2-sulfatase, ceramidase,galactocerebrosidase, β-glucuronidase, Heparan N-sulfatase,N-Acetyl-α-glucosaminidase, Acetyl CoA-α-glucosaminide N-acetyltransferase, N-acetyl-glucosamine-6 sulfatase, Galactose 6-sulfatase,Arylsulfatase A, B, or C, Arylsulfatase A Cerebroside, Ganglioside, Acidβ-galactosidase G_(MI) Gaiglioside, Acid β-galactosidase, HexosaminidaseA, Hexosaminidase B, α-fucosidase, α-N-Acetyl galactosaminidase,Glycoprotein Neuraminidase, Aspartylglucosamine amidase, Acid Lipase,Acid Ceramidase, Lysosomal Sphingomyelinase other Sphingomyelinase,dystrophin, components of dystrophin-glycoprotein complex, thelaminin-α2 chain, fukutin-related protein, LARGE, fukutin, EMD, LMNA,DMPK, ZNF9, and PABPN1, Glycogen synthase, Glucose-6-phosphatase,Debranching enzyme, Transglucosidase, Myophosphorylase, Phosphorylase,Phosphofructokinase, Acid Maltase Deficiency, Carnitine PalmitylTransferase, Phosphoglycerate Kinase, or Phosphoglycerate Mutase.